From d8bbc7858622b6d9c278469aab701ca0b609cddf Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 15 May 2024 05:35:49 +0200
Subject: Merging upstream version 126.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../checkout/conformance2/00_test_list.txt         |   1 +
 .../checkout/conformance2/canvas/00_test_list.txt  |   1 +
 .../canvas/drawingbuffer-storage-test.html         |  27 ++
 .../conformance2/extensions/00_test_list.txt       |  11 +
 .../extensions/ext-conservative-depth.html         | 145 +++++++
 .../ext-disjoint-timer-query-webgl2.html           |  58 +++
 .../conformance2/extensions/ext-render-snorm.html  | 201 +++++++++
 .../nv-shader-noperspective-interpolation.html     | 251 +++++++++++
 .../extensions/oes-sample-variables.html           | 474 ++++++++++++++++++++
 .../oes-shader-multisample-interpolation.html      | 313 ++++++++++++++
 .../extensions/webgl-blend-func-extended.html      |  26 ++
 .../extensions/webgl-clip-cull-distance.html       | 475 +++++++++++++++++++++
 .../extensions/webgl-provoking-vertex.html         | 165 +++++++
 .../extensions/webgl-render-shared-exponent.html   | 251 +++++++++++
 .../webgl-shader-pixel-local-storage.html          | 445 +++++++++++++++++++
 .../extensions/webgl-stencil-texturing.html        | 279 ++++++++++++
 .../checkout/conformance2/glsl3/00_test_list.txt   |   1 +
 .../checkout/conformance2/glsl3/texture-bias.html  | 146 +++++++
 .../checkout/conformance2/query/00_test_list.txt   |   1 +
 .../query/occlusion-query-scissor.html             | 117 +++++
 .../framebuffer-object-attachment.html             | 112 ++++-
 .../renderbuffers/framebuffer-texture-layer.html   |  31 ++
 .../conformance2/rendering/00_test_list.txt        |   1 -
 .../rendering/builtin-vert-attribs.html            | 408 ------------------
 .../conformance2/textures/misc/00_test_list.txt    |   1 +
 .../textures/misc/tex-image-10bpc.html             |  66 +++
 .../tex-image-with-bad-args-from-dom-elements.html |   1 -
 .../textures/misc/tex-new-formats.html             |  30 ++
 .../transform_feedback/simultaneous_binding.html   |  11 +
 .../transform_feedback/transform_feedback.html     |  66 +++
 .../checkout/conformance2/wasm/00_test_list.txt    |  12 +
 .../wasm/bufferdata-16gb-wasm-memory.html          |  51 +++
 .../wasm/bufferdata-4gb-wasm-memory.html           |  51 +++
 .../wasm/buffersubdata-16gb-wasm-memory.html       |  52 +++
 .../wasm/buffersubdata-4gb-wasm-memory.html        |  52 +++
 .../wasm/getbuffersubdata-16gb-wasm-memory.html    |  48 +++
 .../wasm/getbuffersubdata-4gb-wasm-memory.html     |  48 +++
 .../wasm/readpixels-16gb-wasm-memory.html          |  51 +++
 .../wasm/readpixels-4gb-wasm-memory.html           |  50 +++
 .../wasm/teximage2d-16gb-wasm-memory.html          |  85 ++++
 .../wasm/teximage2d-4gb-wasm-memory.html           |  85 ++++
 .../wasm/texsubimage2d-16gb-wasm-memory.html       |  86 ++++
 .../wasm/texsubimage2d-4gb-wasm-memory.html        |  86 ++++
 43 files changed, 4443 insertions(+), 429 deletions(-)
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/canvas/drawingbuffer-storage-test.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-conservative-depth.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-render-snorm.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/nv-shader-noperspective-interpolation.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-sample-variables.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-shader-multisample-interpolation.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-blend-func-extended.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-clip-cull-distance.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-provoking-vertex.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-render-shared-exponent.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-shader-pixel-local-storage.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-stencil-texturing.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/texture-bias.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/query/occlusion-query-scissor.html
 delete mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/rendering/builtin-vert-attribs.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-10bpc.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/00_test_list.txt
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-16gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-4gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-16gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-4gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-16gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-4gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-16gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-4gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-16gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-4gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-16gb-wasm-memory.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-4gb-wasm-memory.html

(limited to 'dom/canvas/test/webgl-conf/checkout/conformance2')

diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/00_test_list.txt
index e251dc9758..fabc72c1da 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/00_test_list.txt
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/00_test_list.txt
@@ -18,3 +18,4 @@ textures/00_test_list.txt
 transform_feedback/00_test_list.txt
 uniforms/00_test_list.txt
 vertex_arrays/00_test_list.txt
+--min-version 2.0.1 wasm/00_test_list.txt
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/canvas/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/canvas/00_test_list.txt
index 35e011f3bf..878a2797c4 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/canvas/00_test_list.txt
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/canvas/00_test_list.txt
@@ -1 +1,2 @@
+--min-version 2.0.1 drawingbuffer-storage-test.html
 --min-version 2.0.1 to-data-url-with-pack-params.html
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/canvas/drawingbuffer-storage-test.html b/dom/canvas/test/webgl-conf/checkout/conformance2/canvas/drawingbuffer-storage-test.html
new file mode 100644
index 0000000000..6f18d441c0
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/canvas/drawingbuffer-storage-test.html
@@ -0,0 +1,27 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL2 drawingBufferStorage Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+<script src="../../js/tests/drawingbuffer-storage-test.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+runTest(2);
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/00_test_list.txt
index 559071ff06..2cc4456ecb 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/00_test_list.txt
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/00_test_list.txt
@@ -1,11 +1,16 @@
 ext-color-buffer-float.html
 --min-version 2.0.1 ext-color-buffer-half-float.html
+--min-version 2.0.1 ext-conservative-depth.html
 ext-disjoint-timer-query-webgl2.html
+--min-version 2.0.1 ext-render-snorm.html
 --min-version 2.0.1 ext-texture-filter-anisotropic.html
 --min-version 2.0.1 ext-texture-norm16.html
 promoted-extensions.html
 promoted-extensions-in-shaders.html
+--min-version 2.0.1 nv-shader-noperspective-interpolation.html
 --min-version 2.0.1 oes-draw-buffers-indexed.html
+--min-version 2.0.1 oes-sample-variables.html
+--min-version 2.0.1 oes-shader-multisample-interpolation.html
 --min-version 2.0.1 ovr_multiview2.html
 --min-version 2.0.1 ovr_multiview2_depth.html
 --min-version 2.0.1 ovr_multiview2_draw_buffers.html
@@ -16,4 +21,10 @@ promoted-extensions-in-shaders.html
 --min-version 2.0.1 ovr_multiview2_timer_query.html
 --min-version 2.0.1 ovr_multiview2_transform_feedback.html
 --min-version 2.0.1 required-extensions.html
+--min-version 2.0.1 webgl-blend-func-extended.html
+--min-version 2.0.1 webgl-clip-cull-distance.html
 --min-version 2.0.1 webgl-multi-draw-instanced-base-vertex-base-instance.html
+--min-version 2.0.1 webgl-provoking-vertex.html
+--min-version 2.0.1 webgl-render-shared-exponent.html
+--min-version 2.0.1 webgl-shader-pixel-local-storage.html
+--min-version 2.0.1 webgl-stencil-texturing.html
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-conservative-depth.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-conservative-depth.html
new file mode 100644
index 0000000000..c9c9f85bdb
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-conservative-depth.html
@@ -0,0 +1,145 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL EXT_conservative_depth Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas width="32" height="32" id="c"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the EXT_conservative_depth extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext("c", null, 2);
+var ext;
+
+function runShaderTests(extensionEnabled) {
+    debug("");
+    debug("Testing various shader compiles with extension " + (extensionEnabled ? "enabled" : "disabled"));
+
+    const macro = `#version 300 es
+        precision mediump float;
+        out vec4 my_FragColor;
+        void main() {
+        #ifdef GL_EXT_conservative_depth
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        #else
+            #error no GL_EXT_conservative_depth;
+        #endif
+        }`;
+
+    const missingExtension = `#version 300 es
+        precision mediump float;
+        out vec4 my_FragColor;
+        layout (depth_any) out float gl_FragDepth;
+        void main() {
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+            gl_FragDepth = 1.0;
+        }`;
+
+    const valid = `#version 300 es
+        #extension GL_EXT_conservative_depth : enable
+        precision mediump float;
+        out vec4 my_FragColor;
+        layout (depth_any) out float gl_FragDepth;
+        void main() {
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+            gl_FragDepth = 1.0;
+        }`;
+
+    const invalid = `#version 300 es
+        #extension GL_EXT_conservative_depth : enable
+        precision mediump float;
+        out vec4 my_FragColor;
+        layout (depth_unchanged) out float gl_FragDepth;
+        void main() {
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+            gl_FragDepth = 1.0;
+        }`;
+
+    // Always expect the shader missing the #extension pragma to fail (whether enabled or not)
+    if (wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, missingExtension])) {
+        testFailed("Depth layout qualifier allowed without #extension pragma");
+    } else {
+        testPassed("Depth layout qualifier disallowed without #extension pragma");
+    }
+
+    // Expect the macro shader to succeed ONLY if enabled
+    if (wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, macro])) {
+        if (extensionEnabled) {
+            testPassed("Macro defined in shaders when extension is enabled");
+        } else {
+            testFailed("Macro defined in shaders when extension is disabled");
+        }
+    } else {
+        if (extensionEnabled) {
+            testFailed("Macro not defined in shaders when extension is enabled");
+        } else {
+            testPassed("Macro not defined in shaders when extension is disabled");
+        }
+    }
+
+    // Try to compile a shader using a layout qualifier that should only succeed if enabled
+    if (wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, valid])) {
+        if (extensionEnabled) {
+            testPassed("Depth layout qualifier compiled successfully when extension enabled");
+        } else {
+            testFailed("Depth layout qualifier compiled successfully when extension disabled");
+        }
+    } else {
+        if (extensionEnabled) {
+            testFailed("Depth layout qualifier failed to compile when extension enabled");
+        } else {
+            testPassed("Depth layout qualifier failed to compile when extension disabled");
+        }
+    }
+
+    // Try to compile a shader using a disallowed layout qualifier
+    if (wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, invalid])) {
+        testFailed("Unsupported depth layout qualifier compiled successfully");
+    } else {
+        testPassed("Unsupported depth layout qualifier failed to compile");
+    }
+}
+
+function runTest() {
+    if (!gl) {
+        testFailed("WebGL context does not exist");
+        return;
+    }
+    testPassed("WebGL context exists");
+
+    runShaderTests(false);
+
+    ext = gl.getExtension("EXT_conservative_depth");
+    wtu.runExtensionSupportedTest(gl, "EXT_conservative_depth", ext !== null);
+
+    if (!ext) {
+        testPassed("No EXT_conservative_depth support -- this is legal");
+    } else {
+        testPassed("Successfully enabled EXT_conservative_depth extension");
+        runShaderTests(true);
+    }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-disjoint-timer-query-webgl2.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-disjoint-timer-query-webgl2.html
index c051fa36a3..f1e9a82d8a 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-disjoint-timer-query-webgl2.html
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-disjoint-timer-query-webgl2.html
@@ -25,7 +25,9 @@ description("This test verifies the functionality of the EXT_disjoint_timer_quer
 var wtu = WebGLTestUtils;
 var canvas = document.getElementById("canvas");
 var gl = wtu.create3DContext(canvas, null, 2);
+var gl2 = null;
 var ext = null;
+var ext2 = null;
 var query = null;
 var query2 = null;
 var elapsed_query = null;
@@ -62,6 +64,8 @@ if (!gl) {
             wtu.glErrorShouldBe(gl, gl.NO_ERROR);
         }
         verifyQueryResultsNotAvailable();
+        verifyDeleteQueryBehavior();
+        verifyDeleteQueryErrorBehavior();
         wtu.glErrorShouldBe(gl, gl.NO_ERROR);
 
         window.requestAnimationFrame(checkQueryResults);
@@ -249,6 +253,60 @@ function verifyQueryResultsNotAvailable() {
     testPassed("Queries' results didn't become available in a spin loop");
 }
 
+function verifyDeleteQueryBehavior() {
+    debug("");
+    debug("Testing deleting an active query should end it.");
+
+    // Use a new context for this test
+    gl2 = wtu.create3DContext(null, null, 2);
+    if (!gl2) return;
+    ext2 = gl2.getExtension("EXT_disjoint_timer_query_webgl2");
+    if (!ext2) return;
+
+    query = gl2.createQuery();
+    gl2.beginQuery(ext.TIME_ELAPSED_EXT, query);
+    wtu.glErrorShouldBe(gl2, gl2.NONE, "The query began successfully");
+    gl2.deleteQuery(query);
+    wtu.glErrorShouldBe(gl2, gl2.NONE, "Deletion of the active query succeeds");
+    shouldBeNull("gl2.getQuery(ext2.TIME_ELAPSED_EXT, gl2.CURRENT_QUERY)");
+    shouldBeFalse("gl2.isQuery(query)");
+    query = gl2.createQuery();
+    gl2.beginQuery(ext2.TIME_ELAPSED_EXT, query);
+    wtu.glErrorShouldBe(gl, gl2.NONE, "Beginning a new query succeeds");
+    gl2.endQuery(gl2.TIME_ELAPSED_EXT);
+    gl2.deleteQuery(query);
+    wtu.glErrorShouldBe(gl, gl.NONE);
+    query = null;
+    ext2 = null;
+    gl2 = null;
+}
+
+function verifyDeleteQueryErrorBehavior() {
+    debug("");
+    debug("Testing deleting a query created by another context.");
+
+    // Use new contexts for this test
+    gl2 = wtu.create3DContext(null, null, 2);
+    var gl3 = wtu.create3DContext(null, null, 2);
+    if (!gl2 || !gl3) return;
+    ext2 = gl2.getExtension("EXT_disjoint_timer_query_webgl2");
+    if (!ext2) return;
+
+    query = gl2.createQuery();
+    gl2.beginQuery(ext2.TIME_ELAPSED_EXT, query);
+    gl3.deleteQuery(query);
+    wtu.glErrorShouldBe(gl3, gl3.INVALID_OPERATION);
+    shouldBeTrue("gl2.isQuery(query)");
+    shouldBe("gl2.getQuery(ext2.TIME_ELAPSED_EXT, gl2.CURRENT_QUERY)", "query");
+    gl2.endQuery(ext2.TIME_ELAPSED_EXT);
+    gl2.deleteQuery(query);
+    wtu.glErrorShouldBe(gl2, gl2.NONE);
+    query = null;
+    ext2 = null;
+    gl2 = null;
+    gl3 = null;
+}
+
 function checkQueryResults() {
     if (availability_retry > 0) {
         // Make a reasonable attempt to wait for the queries' results to become available.
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-render-snorm.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-render-snorm.html
new file mode 100644
index 0000000000..723e762773
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/ext-render-snorm.html
@@ -0,0 +1,201 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL EXT_render_snorm Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the EXT_render_snorm extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext(null, null, 2);
+var ext;
+
+function createTypedArray(type) {
+    switch (type) {
+        case gl.BYTE:
+            return new Int8Array(4);
+        case gl.UNSIGNED_BYTE:
+            return new Uint8Array(4);
+        case gl.SHORT:
+            return new Int16Array(4);
+        case gl.UNSIGNED_SHORT:
+            return new Uint16Array(4);
+        default:
+            return null;
+    }
+}
+
+function drawTest(config) {
+    wtu.drawUnitQuad(gl);
+
+    const implementationType = gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_TYPE);
+    const implementationFormat = gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_FORMAT);
+
+    // Support for reading signed data with unsigned read type is not required
+    // but implementations may allow such conversions. Do not expect the error
+    // when the type matches the buffer type or when it's explicitly supported.
+    for (const type of [gl.BYTE, gl.UNSIGNED_BYTE, gl.SHORT, gl.UNSIGNED_SHORT]) {
+        if (type == config.type) continue;
+        if (implementationFormat != gl.RGBA || implementationType != type) {
+            gl.readPixels(0, 0, 1, 1, gl.RGBA, type, createTypedArray(type));
+            wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "reading with unsupported type fails");
+        }
+    }
+
+    const defaultPixel = createTypedArray(config.type);
+    wtu.checkCanvasRect(gl, 0, 0, 1, 1, config.color,
+                        "reading with the RGBA format and matching type", 1,
+                        defaultPixel,
+                        config.type, gl.RGBA);
+
+    if (implementationFormat == config.format && implementationType == config.type) {
+        const implementationPixel = createTypedArray(implementationType);
+        const color = [config.color[0]];
+        if (config.format != gl.RED) color.push(config.color[1]);
+        if (config.format == gl.RGBA) color.push(config.color[2], config.color[3]);
+        wtu.checkCanvasRect(gl, 0, 0, 1, 1, color,
+                            "reading with the exact format/type", 1,
+                            implementationPixel,
+                            implementationType, implementationFormat);
+    }
+}
+
+function renderbufferTest(config, isSupported) {
+    debug("");
+    debug(`${config.name} renderbuffer: ` +
+          `${!isSupported || !config.color ? "NOT " : ""}supported`);
+
+    const rbo = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+    gl.renderbufferStorage(gl.RENDERBUFFER, config.internalFormat, 1, 1);
+    if (!isSupported || !config.color) {
+        wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "renderbuffer allocation failed");
+        return;
+    }
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "renderbuffer allocation succeeded");
+
+    const fbo = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+    wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+    drawTest(config);
+}
+
+function textureTest(config, isRenderable, isTexturable) {
+    debug("");
+    debug(`${config.name} texture: ` +
+          `${!isRenderable || !config.color ? "NOT " : ""}renderable, ` +
+          `${!isTexturable ? "NOT " : ""}texturable`);
+
+    const tex = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, tex);
+    gl.texImage2D(gl.TEXTURE_2D, 0, config.internalFormat, 1, 1, 0, config.format, config.type, null);
+    if (!isTexturable) {
+        wtu.glErrorShouldBe(gl,
+                            [gl.INVALID_ENUM, gl.INVALID_VALUE, gl.INVALID_OPERATION],
+                            "texture allocation failed");
+        return;
+    }
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "texture allocation succeeded");
+
+    const fbo = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
+
+    if (!isRenderable || !config.color) {
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_INCOMPLETE_ATTACHMENT);
+        return;
+    }
+    wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+    drawTest(config);
+}
+
+function formatTest(isSnormEnabled, isNorm16Enabled) {
+    const program = wtu.setupProgram(gl, [wtu.simpleVertexShader,
+                                          wtu.simpleColorFragmentShader]);
+    gl.useProgram(program);
+    gl.uniform4f(gl.getUniformLocation(program, "u_color"), -0.0625, -0.125, -0.25, -0.5);
+
+    wtu.setupUnitQuad(gl);
+
+    const configs8 = [
+        {name: "R8_SNORM",    format: gl.RED,  type: gl.BYTE, internalFormat: gl.R8_SNORM,    color: [-8,   0,   0, 127]},
+        {name: "RG8_SNORM",   format: gl.RG,   type: gl.BYTE, internalFormat: gl.RG8_SNORM,   color: [-8, -16,   0, 127]},
+        {name: "RGB8_SNORM",  format: gl.RGB,  type: gl.BYTE, internalFormat: gl.RGB8_SNORM,  color: null},
+        {name: "RGBA8_SNORM", format: gl.RGBA, type: gl.BYTE, internalFormat: gl.RGBA8_SNORM, color: [-8, -16, -32, -64]}
+    ];
+
+    const configs16 = [
+        {name: "R16_SNORM",    format: gl.RED,  type: gl.SHORT, internalFormat: 0x8F98 /* R16_SNORM_EXT */,    color: [-2048,   0,       0,  32767]},
+        {name: "RG16_SNORM",   format: gl.RG,   type: gl.SHORT, internalFormat: 0x8F99 /* RG16_SNORM_EXT */,   color: [-2048, -4096,     0,  32767]},
+        {name: "RGB16_SNORM",  format: gl.RGB,  type: gl.SHORT, internalFormat: 0x8F9A /* RGB16_SNORM_EXT */,  color: null},
+        {name: "RGBA16_SNORM", format: gl.RGBA, type: gl.SHORT, internalFormat: 0x8F9B /* RGBA16_SNORM_EXT */, color: [-2048, -4096, -8192, -16384]}
+    ];
+
+    for (const config of configs8) {
+        renderbufferTest(config, isSnormEnabled);
+        textureTest(config, isSnormEnabled, true);
+    }
+
+    for (const config of configs16) {
+        renderbufferTest(config, isSnormEnabled && isNorm16Enabled);
+        textureTest(config, isSnormEnabled && isNorm16Enabled, isNorm16Enabled);
+    }
+}
+
+function runTest() {
+    if (!gl) {
+        testFailed("context does not exist");
+        return;
+    }
+
+    testPassed("context exists");
+
+    debug("");
+    debug("Testing signed normalized formats with EXT_render_snorm disabled");
+    formatTest(false, false);
+
+    ext = gl.getExtension("EXT_render_snorm");
+    wtu.runExtensionSupportedTest(gl, "EXT_render_snorm", ext !== null);
+
+    if (ext !== null) {
+        debug("");
+        debug("Testing signed normalized formats with only EXT_render_snorm enabled");
+        formatTest(true, false);
+
+        if (gl.getExtension("EXT_texture_norm16")) {
+            debug("");
+            debug("Testing signed normalized formats with EXT_render_snorm and EXT_texture_norm16 enabled");
+            formatTest(true, true);
+        }
+    } else {
+        testPassed("No EXT_render_snorm support -- this is legal");
+    }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/nv-shader-noperspective-interpolation.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/nv-shader-noperspective-interpolation.html
new file mode 100644
index 0000000000..2198c17b1a
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/nv-shader-noperspective-interpolation.html
@@ -0,0 +1,251 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL NV_shader_noperspective_interpolation Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas width="128" height="128" id="c"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the NV_shader_noperspective_interpolation extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext("c", null, 2);
+var ext;
+
+function runShaderTests(extensionEnabled) {
+    debug("");
+    debug("Testing various shader compiles with extension " + (extensionEnabled ? "enabled" : "disabled"));
+
+    const macroVertex = `#version 300 es
+        in vec4 vPosition;
+        void main() {
+        #ifdef GL_NV_shader_noperspective_interpolation
+            gl_Position = vPosition;
+        #else
+            #error no GL_NV_shader_noperspective_interpolation;
+        #endif
+        }`;
+
+    const macroFragment = `#version 300 es
+        precision highp float;
+        out vec4 my_FragColor;
+        void main() {
+        #ifdef GL_NV_shader_noperspective_interpolation
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        #else
+            #error no GL_NV_shader_noperspective_interpolation;
+        #endif
+        }`;
+
+    for (const shaders of [[wtu.simpleVertexShaderESSL300, macroFragment],
+                           [macroVertex, wtu.simpleColorFragmentShaderESSL300]]) {
+        // Expect the macro shader to succeed ONLY if enabled
+        if (wtu.setupProgram(gl, shaders)) {
+            if (extensionEnabled) {
+                testPassed("Macro defined in shaders when extension is enabled");
+            } else {
+                testFailed("Macro defined in shaders when extension is disabled");
+            }
+        } else {
+            if (extensionEnabled) {
+                testFailed("Macro not defined in shaders when extension is enabled");
+            } else {
+                testPassed("Macro not defined in shaders when extension is disabled");
+            }
+        }
+    }
+
+    const missingVertex = `#version 300 es
+        noperspective out float interpolant;
+        in vec4 vPosition;
+        void main() {
+            gl_Position = vPosition;
+        }`;
+
+    const missingFragment = `#version 300 es
+        precision highp float;
+        noperspective in float interpolant;
+        out vec4 my_FragColor;
+        void main() {
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        }`;
+
+    // Always expect the shader missing the #extension pragma to fail (whether enabled or not)
+    for (const shaders of [[missingVertex, wtu.simpleColorFragmentShaderESSL300],
+                           [wtu.simpleVertexShaderESSL300, missingFragment],
+                           [missingVertex, missingFragment]]) {
+        if (wtu.setupProgram(gl, shaders)) {
+            testFailed("Noperspective interpolation qualifier allowed without #extension pragma");
+        } else {
+            testPassed("Noperspective interpolation qualifier disallowed without #extension pragma");
+        }
+    }
+
+    const validVertex = `#version 300 es
+        #extension GL_NV_shader_noperspective_interpolation : enable
+        noperspective out float interpolant;
+        in vec4 vPosition;
+        void main() {
+            gl_Position = vPosition;
+        }`;
+
+    const validFragment = `#version 300 es
+        #extension GL_NV_shader_noperspective_interpolation : enable
+        precision highp float;
+        noperspective in float interpolant;
+        out vec4 my_FragColor;
+        void main() {
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        }`;
+
+    // Try to compile a shader using a noperspective qualifier that should only succeed if enabled
+    if (wtu.setupProgram(gl, [validVertex, validFragment])) {
+        if (extensionEnabled) {
+            testPassed("Noperspective interpolation qualifier compiled successfully when extension enabled");
+        } else {
+            testFailed("Noperspective interpolation qualifier compiled successfully when extension disabled");
+        }
+    } else {
+        if (extensionEnabled) {
+            testFailed("Noperspective interpolation qualifier failed to compile when extension enabled");
+        } else {
+            testPassed("Noperspective interpolation qualifier failed to compile when extension disabled");
+        }
+    }
+
+    debug("");
+}
+
+function runInterpolationTest() {
+    function draw(program, skew) {
+        gl.useProgram(program);
+
+        const posLoc = gl.getAttribLocation(program, "position");
+        const colLoc = gl.getAttribLocation(program, "color");
+
+        const buf = gl.createBuffer();
+        gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+        gl.bufferData(
+            gl.ARRAY_BUFFER,
+            new Float32Array([
+                -1.0, -1.0,        0.0, 1.0,
+                +1.0, -1.0,        0.0, 1.0,
+                 0.0, +1.0 * skew, 0.0, skew,
+
+                 1.0, 0.0, 0.0, 1.0,
+                 0.0, 1.0, 0.0, 1.0,
+                 0.0, 0.0, 1.0, 1.0]),
+            gl.STATIC_DRAW);
+
+        gl.vertexAttribPointer(posLoc, 4, gl.FLOAT, false, 0, 0);
+        gl.vertexAttribPointer(colLoc, 4, gl.FLOAT, false, 0, 48);
+        gl.enableVertexAttribArray(posLoc);
+        gl.enableVertexAttribArray(colLoc);
+        gl.drawArrays(gl.TRIANGLES, 0, 3);
+    }
+
+    const vertexSmooth = `#version 300 es
+        in vec4 position;
+        in vec4 color;
+        smooth out vec4 interp_color;
+        void main() {
+            gl_Position = position;
+            interp_color = color;
+        }`;
+
+    const fragmentSmooth = `#version 300 es
+        precision highp float;
+        smooth in vec4 interp_color;
+        out vec4 fragColor;
+        void main() {
+            fragColor = interp_color;
+        }`;
+    const programSmooth = wtu.setupProgram(gl, [vertexSmooth, fragmentSmooth]);
+
+    debug("Get non-skewed value with smooth interpolation");
+    gl.clearColor(0.0, 0.0, 0.0, 1.0);
+    gl.clear(gl.COLOR_BUFFER_BIT);
+    draw(programSmooth, 1.0);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+    const smoothColor = new Uint8Array(4);
+    gl.readPixels(64, 64, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, smoothColor);
+
+    const vertexNoperspective = `#version 300 es
+        #extension GL_NV_shader_noperspective_interpolation : require
+        in vec4 position;
+        in vec4 color;
+        noperspective out vec4 interp_color;
+        void main() {
+            gl_Position = position;
+            interp_color = color;
+        }`;
+
+    const fragmentNoperspective = `#version 300 es
+        #extension GL_NV_shader_noperspective_interpolation : require
+        precision highp float;
+        noperspective in vec4 interp_color;
+        out vec4 fragColor;
+        void main() {
+            fragColor = interp_color;
+        }`;
+    const programNoperspective = wtu.setupProgram(gl, [vertexNoperspective, fragmentNoperspective]);
+
+    debug("");
+    debug("Check non-skewed value with noperspective interpolation");
+    gl.clear(gl.COLOR_BUFFER_BIT);
+    draw(programNoperspective, 1.0);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    wtu.checkCanvasRect(gl, 64, 64, 1, 1, smoothColor, "Non-skewed noperspective should match smooth");
+
+    debug("");
+    debug("Check skewed value with noperspective interpolation");
+    gl.clear(gl.COLOR_BUFFER_BIT);
+    draw(programNoperspective, 2.0);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    wtu.checkCanvasRect(gl, 64, 64, 1, 1, smoothColor, "Skewed noperspective should match smooth");
+}
+
+function runTest() {
+    if (!gl) {
+        testFailed("WebGL context does not exist");
+        return;
+    }
+    testPassed("WebGL context exists");
+
+    runShaderTests(false);
+
+    ext = gl.getExtension("NV_shader_noperspective_interpolation");
+    wtu.runExtensionSupportedTest(gl, "NV_shader_noperspective_interpolation", ext !== null);
+
+    if (!ext) {
+        testPassed("No NV_shader_noperspective_interpolation support -- this is legal");
+    } else {
+        testPassed("Successfully enabled NV_shader_noperspective_interpolation extension");
+        runShaderTests(true);
+        runInterpolationTest();
+    }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-sample-variables.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-sample-variables.html
new file mode 100644
index 0000000000..41fc8f8242
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-sample-variables.html
@@ -0,0 +1,474 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL OES_sample_variables Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas width="32" height="32" id="c"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the OES_sample_variables extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext("c", { antialias: false }, 2);
+var ext;
+
+function runShaderTests(extensionEnabled) {
+    debug("");
+    debug("Testing various shader compiles with extension " + (extensionEnabled ? "enabled" : "disabled"));
+
+    const macro = `#version 300 es
+        precision highp float;
+        out vec4 my_FragColor;
+        void main() {
+        #ifdef GL_OES_sample_variables
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        #else
+            #error no GL_OES_sample_variables;
+        #endif
+        }`;
+
+    // Expect the macro shader to succeed ONLY if enabled
+    if (wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, macro])) {
+        if (extensionEnabled) {
+            testPassed("Macro defined in shaders when extension is enabled");
+        } else {
+            testFailed("Macro defined in shaders when extension is disabled");
+        }
+    } else {
+        if (extensionEnabled) {
+            testFailed("Macro not defined in shaders when extension is enabled");
+        } else {
+            testPassed("Macro not defined in shaders when extension is disabled");
+        }
+    }
+
+    const missing = `#version 300 es
+        precision highp float;
+        out vec4 my_FragColor;
+        void main() {
+            gl_SampleMask[0] = gl_SampleMaskIn[0] & 0x55555555;
+            my_FragColor = vec4(gl_SamplePosition.yx, float(gl_SampleID), float(gl_MaxSamples + gl_NumSamples));
+        }`;
+
+    // Always expect the shader missing the #extension pragma to fail (whether enabled or not)
+    if (wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, missing])) {
+        testFailed("Sample variables allowed without #extension pragma");
+    } else {
+        testPassed("Sample variables disallowed without #extension pragma");
+    }
+
+    const valid = `#version 300 es
+        #extension GL_OES_sample_variables : enable
+        precision highp float;
+        out vec4 my_FragColor;
+        void main() {
+            gl_SampleMask[0] = gl_SampleMaskIn[0] & 0x55555555;
+            my_FragColor = vec4(gl_SamplePosition.yx, float(gl_SampleID), float(gl_MaxSamples + gl_NumSamples));
+        }`;
+
+    // Try to compile a shader using sample variables that should only succeed if enabled
+    if (wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, valid])) {
+        if (extensionEnabled) {
+            testPassed("Sample variables compiled successfully when extension enabled");
+        } else {
+            testFailed("Sample variables compiled successfully when extension disabled");
+        }
+    } else {
+        if (extensionEnabled) {
+            testFailed("Sample variables failed to compile when extension enabled");
+        } else {
+            testPassed("Sample variables failed to compile when extension disabled");
+        }
+    }
+
+    debug("");
+}
+
+function runMaxSamplesTest() {
+    debug("");
+    debug("Testing gl_MaxSamples");
+
+    const frag = `#version 300 es
+        #extension GL_OES_sample_variables : require
+        precision highp float;
+        out vec4 color;
+        void main() {
+            color = vec4(float(gl_MaxSamples * 4) / 255.0, 0.0, 0.0, 1.0);
+        }`;
+    gl.useProgram(wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, frag]));
+
+    wtu.setupUnitQuad(gl);
+    wtu.drawUnitQuad(gl);
+
+    wtu.checkCanvas(gl, [gl.getParameter(gl.MAX_SAMPLES) * 4, 0, 0, 255], "should match MAX_SAMPLES", 1);
+}
+
+function runNumSamplesTest() {
+    debug("");
+    debug("Testing gl_NumSamples");
+
+    const rbo = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+    gl.renderbufferStorageMultisample(gl.RENDERBUFFER, 4, gl.RGBA8, 32, 32);
+
+    const fbo = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+    wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+    const frag = `#version 300 es
+        #extension GL_OES_sample_variables : require
+        precision highp float;
+        out vec4 color;
+        void main() {
+            if (gl_NumSamples == 4) {
+                color = vec4(0.0, 1.0, 0.0, 1.0);
+            } else {
+                color = vec4(1.0, 0.0, 0.0, 1.0);
+            }
+        }`;
+    gl.useProgram(wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, frag]));
+
+    wtu.setupUnitQuad(gl);
+    wtu.drawUnitQuad(gl);
+
+    gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fbo);
+    gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
+    gl.blitFramebuffer(0, 0, 32, 32, 0, 0, 32, 32, gl.COLOR_BUFFER_BIT, gl.NEAREST);
+
+    gl.bindFramebuffer(gl.READ_FRAMEBUFFER, null);
+    wtu.checkCanvas(gl, [0, 255, 0, 255], "should be green");
+}
+
+function runSampleIDTest() {
+    debug("");
+    debug("Testing gl_SampleID");
+
+    const frag = `#version 300 es
+        #extension GL_OES_sample_variables : require
+        precision highp float;
+        out vec4 color;
+        uniform int id;
+        void main() {
+            // Special value when the selected sample is processed, 0.0 otherwise
+            float r = float(gl_SampleID == id ? (1 << gl_SampleID) : 0) * 32.0 / 255.0;
+            // Must always be 0.0
+            float g = float(gl_SampleID < 0 || gl_SampleID >= gl_NumSamples);
+            color = vec4(r, g, 0.0, 1.0);
+        }`;
+    const program = wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, frag]);
+    gl.useProgram(program);
+
+    wtu.setupUnitQuad(gl);
+
+    const rbo = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+    gl.renderbufferStorageMultisample(gl.RENDERBUFFER, 4, gl.RGBA8, 32, 32);
+
+    const fbo = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+    wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+    for (let sample = 0; sample < 4; sample++) {
+        debug(`Sample ${sample} is selected`);
+
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, fbo);
+        gl.uniform1i(gl.getUniformLocation(program, "id"), sample);
+        wtu.drawUnitQuad(gl);
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fbo);
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
+        gl.blitFramebuffer(0, 0, 32, 32, 0, 0, 32, 32, gl.COLOR_BUFFER_BIT, gl.NEAREST);
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, null);
+        wtu.checkCanvas(gl, [(1 << sample) * 8, 0, 0, 255], undefined, 1);
+    }
+}
+
+function runSampleMaskInTest() {
+    debug("");
+    debug("Testing gl_SampleMaskIn");
+
+    const frag = `#version 300 es
+        #extension GL_OES_sample_variables : require
+        precision highp float;
+        out vec4 color;
+        uint popcount(uint v) {
+            uint c = 0u;
+            for (; v != 0u; v >>= 1) c += v & 1u;
+            return c;
+        }
+        void main() {
+            float r = float(popcount(uint(gl_SampleMaskIn[0])));
+            color = vec4(r * 4.0 / 255.0, 0, 0, 1);
+        }`;
+
+    const program = wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, frag]);
+    gl.useProgram(program);
+
+    // Use a triangle instead of the WTU's quad
+    // to avoid artifacts along the diagonal
+    const vertices = gl.createBuffer();
+    gl.bindBuffer(gl.ARRAY_BUFFER, vertices);
+    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
+      -1.0,  1.0,
+       1.0, -1.0,
+      -1.0, -1.0]), gl.STATIC_DRAW);
+    gl.enableVertexAttribArray(0);
+    gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
+
+    function test(sampleCount, sampleCoverageEnabled, coverage) {
+        if (sampleCoverageEnabled) {
+            gl.enable(gl.SAMPLE_COVERAGE);
+        } else {
+            gl.disable(gl.SAMPLE_COVERAGE);
+        }
+
+        gl.sampleCoverage(coverage, false);
+
+        const rbo = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+        gl.renderbufferStorageMultisample(gl.RENDERBUFFER, sampleCount, gl.RGBA8, 32, 32);
+
+        const fbo = gl.createFramebuffer();
+        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, fbo);
+        gl.clear(gl.COLOR_BUFFER_BIT);
+        gl.drawArrays(gl.TRIANGLES, 0, 3);
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fbo);
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
+        gl.blitFramebuffer(0, 0, 32, 32, 0, 0, 32, 32, gl.COLOR_BUFFER_BIT, gl.NEAREST);
+
+        // Shader scales up the number of input samples to increase precision in unorm8 space.
+        let expected = Math.max(sampleCount, 1) * 4;
+
+        // Sample coverage must not affect single sampled buffers
+        if (sampleCoverageEnabled && sampleCount > 0) {
+            // The number of samples in gl_SampleMaskIn must be affected by the sample
+            // coverage GL state and then the resolved value must be scaled down again.
+            expected *= coverage * coverage;
+        }
+
+        // Check only the red channel
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, null);
+        const pixel = new Uint8Array(4);
+        gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, pixel);
+        const message = `Expected: ${expected}, Actual: ${pixel[0]}, ` +
+                        `Samples: ${sampleCount}, Sample Coverage: ${sampleCoverageEnabled}, Coverage: ${coverage}`;
+        if (Math.abs(pixel[0] - expected) > 2) {
+            testFailed(message);
+        } else {
+            testPassed(message);
+        }
+    }
+
+    // Include all exposed sample counts and additionally test single-sampled rendering
+    const sampleCounts = [...gl.getInternalformatParameter(gl.RENDERBUFFER, gl.RGBA8, gl.SAMPLES), 0];
+
+    for (const sampleCount of sampleCounts) {
+        if (sampleCount > 32) {
+            // This test will not work with more than 32 samples.
+            continue;
+        }
+
+        for (const sampleCoverageEnabled of [false, true]) {
+            for (const coverage of [0.0, 0.5, 1.0]) {
+                if (sampleCount == 1 && coverage != 0.0 && coverage != 1.0) {
+                    continue;
+                }
+                test(sampleCount, sampleCoverageEnabled, coverage);
+            }
+        }
+    }
+}
+
+function runSampleMaskInPerSampleTest() {
+    debug("");
+    debug("Testing gl_SampleMaskIn with per-sample shading");
+
+    const frag = `#version 300 es
+        #extension GL_OES_sample_variables : require
+        precision highp float;
+        out vec4 color;
+        void main() {
+            float r = float(gl_SampleMaskIn[0] == (1 << gl_SampleID));
+            color = vec4(r, 0, 0, 1);
+        }`;
+    const program = wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, frag]);
+    gl.useProgram(program);
+
+    wtu.setupUnitQuad(gl);
+
+    // Include all exposed sample counts and additionally test single-sampled rendering
+    const sampleCounts = [...gl.getInternalformatParameter(gl.RENDERBUFFER, gl.RGBA8, gl.SAMPLES), 0];
+    for (const sampleCount of sampleCounts) {
+        if (sampleCount > 32) {
+            // This test will not work with more than 32 samples.
+            continue;
+        }
+
+        const rbo = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+        gl.renderbufferStorageMultisample(gl.RENDERBUFFER, sampleCount, gl.RGBA8, 32, 32);
+
+        const fbo = gl.createFramebuffer();
+        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, fbo);
+        wtu.drawUnitQuad(gl);
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fbo);
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
+        gl.blitFramebuffer(0, 0, 32, 32, 0, 0, 32, 32, gl.COLOR_BUFFER_BIT, gl.NEAREST);
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, null);
+        wtu.checkCanvas(gl, [255, 0, 0, 255], `Samples: ${sampleCount}`, 1);
+    }
+}
+
+function runSampleMaskTest() {
+    debug("");
+    debug("Testing gl_SampleMask");
+
+    const frag = `#version 300 es
+        #extension GL_OES_sample_variables : require
+        precision highp float;
+        uniform highp int sampleMask;
+        out vec4 color;
+        void main() {
+            gl_SampleMask[0] = sampleMask;
+            color = vec4(1, 0, 0, 1);
+        }`;
+    const program = wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, frag]);
+    gl.useProgram(program);
+
+    // Use a triangle instead of the WTU's quad
+    // to avoid artifacts along the diagonal
+    const vertices = gl.createBuffer();
+    gl.bindBuffer(gl.ARRAY_BUFFER, vertices);
+    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
+      -1.0,  1.0,
+       1.0, -1.0,
+      -1.0, -1.0]), gl.STATIC_DRAW);
+    gl.enableVertexAttribArray(0);
+    gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
+
+    function test(sampleCount, sampleMask) {
+        const rbo = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+        gl.renderbufferStorageMultisample(gl.RENDERBUFFER, sampleCount, gl.RGBA8, 32, 32);
+
+        const fbo = gl.createFramebuffer();
+        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, fbo);
+        gl.clear(gl.COLOR_BUFFER_BIT);
+        gl.uniform1i(gl.getUniformLocation(program, "sampleMask"), sampleMask);
+        gl.drawArrays(gl.TRIANGLES, 0, 3);
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fbo);
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
+        gl.blitFramebuffer(0, 0, 32, 32, 0, 0, 32, 32, gl.COLOR_BUFFER_BIT, gl.NEAREST);
+
+        let expected = 1.0;
+        if (sampleCount > 0) {
+            let mask = sampleMask & ((1 << Math.max(sampleCount, 1)) - 1);
+            let bits = 0;
+            for (; mask != 0; mask >>= 1) bits += mask & 1;
+            expected = bits / Math.max(sampleCount, 1);
+        }
+        expected *= 255;
+
+        // Check only the red channel
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, null);
+        const pixel = new Uint8Array(4);
+        gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, pixel);
+        const message = `Samples: ${sampleCount}, `
+                        + `gl_SampleMask[0]: 0x${sampleMask.toString(16).padStart(8, "0").toUpperCase()}, `
+                        + `Actual: ${pixel[0]}, Expected: ${expected}`;
+        if (Math.abs(pixel[0] - expected) > 2) {
+            testFailed(message);
+        } else {
+            testPassed(message);
+        }
+    }
+
+    // Include all exposed sample counts and additionally test single-sampled rendering
+    const sampleCounts = [...gl.getInternalformatParameter(gl.RENDERBUFFER, gl.RGBA8, gl.SAMPLES), 0];
+
+    for (const sampleCount of sampleCounts) {
+        if (sampleCount > 31) {
+            // This test will not work with more than 31 samples.
+            continue;
+        }
+
+        for (const sampleMask of [0xFFFFFFFF, 0x55555555, 0xAAAAAAAA, 0x00000000]) {
+            test(sampleCount, sampleMask);
+        }
+    }
+}
+
+function runTest() {
+    if (!gl) {
+        testFailed("WebGL context does not exist");
+        return;
+    }
+    testPassed("WebGL context exists");
+
+    runShaderTests(false);
+
+    ext = gl.getExtension("OES_sample_variables");
+    wtu.runExtensionSupportedTest(gl, "OES_sample_variables", ext !== null);
+
+    if (!ext) {
+        testPassed("No OES_sample_variables support -- this is legal");
+    } else {
+        testPassed("Successfully enabled OES_sample_variables extension");
+        runShaderTests(true);
+
+        debug("Testing sample variables");
+        runMaxSamplesTest();
+        runNumSamplesTest();
+        runSampleIDTest();
+        runSampleMaskInTest();
+        runSampleMaskInPerSampleTest();
+        runSampleMaskTest();
+    }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-shader-multisample-interpolation.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-shader-multisample-interpolation.html
new file mode 100644
index 0000000000..dcb272c2f0
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/oes-shader-multisample-interpolation.html
@@ -0,0 +1,313 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL OES_shader_multisample_interpolation Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas width="32" height="32" id="c"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the OES_shader_multisample_interpolation extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext("c", { antialias: false }, 2);
+var ext;
+
+function runShaderTests(extensionEnabled) {
+    debug("");
+    debug("Testing various shader compiles with extension " + (extensionEnabled ? "enabled" : "disabled"));
+
+    const macroVertex = `#version 300 es
+        in vec4 vPosition;
+        void main() {
+        #ifdef GL_OES_shader_multisample_interpolation
+            gl_Position = vPosition;
+        #else
+            #error no GL_OES_shader_multisample_interpolation;
+        #endif
+        }`;
+
+    const macroFragment = `#version 300 es
+        precision highp float;
+        out vec4 my_FragColor;
+        void main() {
+        #ifdef GL_OES_shader_multisample_interpolation
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        #else
+            #error no GL_OES_shader_multisample_interpolation;
+        #endif
+        }`;
+
+    for (const shaders of [[wtu.simpleVertexShaderESSL300, macroFragment],
+                           [macroVertex, wtu.simpleColorFragmentShaderESSL300]]) {
+        // Expect the macro shader to succeed ONLY if enabled
+        if (wtu.setupProgram(gl, shaders)) {
+            if (extensionEnabled) {
+                testPassed("Macro defined in shaders when extension is enabled");
+            } else {
+                testFailed("Macro defined in shaders when extension is disabled");
+            }
+        } else {
+            if (extensionEnabled) {
+                testFailed("Macro not defined in shaders when extension is enabled");
+            } else {
+                testPassed("Macro not defined in shaders when extension is disabled");
+            }
+        }
+    }
+
+    const missingVertex = `#version 300 es
+        sample out float interpolant;
+        in vec4 vPosition;
+        void main() {
+            gl_Position = vPosition;
+        }`;
+
+    const missingFragment = `#version 300 es
+        precision highp float;
+        sample in float interpolant;
+        out vec4 my_FragColor;
+        void main() {
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        }`;
+
+    // Always expect the shader missing the #extension pragma to fail (whether enabled or not)
+    for (const shaders of [[missingVertex, wtu.simpleColorFragmentShaderESSL300],
+                           [wtu.simpleVertexShaderESSL300, missingFragment],
+                           [missingVertex, missingFragment]]) {
+        if (wtu.setupProgram(gl, shaders)) {
+            testFailed("Sample interpolation qualifier allowed without #extension pragma");
+        } else {
+            testPassed("Sample interpolation qualifier disallowed without #extension pragma");
+        }
+    }
+
+    const validVertex = `#version 300 es
+        #extension GL_OES_shader_multisample_interpolation : enable
+        sample out float interpolant;
+        in vec4 vPosition;
+        void main() {
+            gl_Position = vPosition;
+        }`;
+
+    const validFragment = `#version 300 es
+        #extension GL_OES_shader_multisample_interpolation : enable
+        precision highp float;
+        sample in float interpolant;
+        out vec4 my_FragColor;
+        void main() {
+            my_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+        }`;
+
+    // Try to compile a shader using a sample qualifier that should only succeed if enabled
+    if (wtu.setupProgram(gl, [validVertex, validFragment])) {
+        if (extensionEnabled) {
+            testPassed("Sample interpolation qualifier compiled successfully when extension enabled");
+        } else {
+            testFailed("Sample interpolation qualifier compiled successfully when extension disabled");
+        }
+    } else {
+        if (extensionEnabled) {
+            testFailed("Sample interpolation qualifier failed to compile when extension enabled");
+        } else {
+            testPassed("Sample interpolation qualifier failed to compile when extension disabled");
+        }
+    }
+}
+
+function runQueryTests(extensionEnabled) {
+    debug("");
+    debug("Testing parameters with extension " + (extensionEnabled ? "enabled" : "disabled"));
+    if (extensionEnabled) {
+        shouldBeGreaterThanOrEqual("gl.getParameter(ext.FRAGMENT_INTERPOLATION_OFFSET_BITS_OES)", "4");
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+        const limit = 0.5 - Math.pow(2, -gl.getParameter(ext.FRAGMENT_INTERPOLATION_OFFSET_BITS_OES));
+        shouldBeLessThanOrEqual("gl.getParameter(ext.MIN_FRAGMENT_INTERPOLATION_OFFSET_OES)", `-${limit}`);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+        shouldBeGreaterThanOrEqual("gl.getParameter(ext.MAX_FRAGMENT_INTERPOLATION_OFFSET_OES)", `${limit}`);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    } else {
+        shouldBeNull("gl.getParameter(0x8E5B /* MIN_FRAGMENT_INTERPOLATION_OFFSET_OES */)");
+        wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+        shouldBeNull("gl.getParameter(0x8E5C /* MAX_FRAGMENT_INTERPOLATION_OFFSET_OES */)");
+        wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+        shouldBeNull("gl.getParameter(0x8E5D /* FRAGMENT_INTERPOLATION_OFFSET_BITS_OES */)");
+        wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    }
+}
+
+function checkEnums() {
+    debug("");
+    debug("Check enums");
+    shouldBe("ext.MIN_FRAGMENT_INTERPOLATION_OFFSET_OES", "0x8E5B");
+    shouldBe("ext.MAX_FRAGMENT_INTERPOLATION_OFFSET_OES", "0x8E5C");
+    shouldBe("ext.FRAGMENT_INTERPOLATION_OFFSET_BITS_OES", "0x8E5D");
+}
+
+/*
+ * This test renders a triangle using MSAAx4 and 1x1 viewport
+ * with the following vertex colors.
+ *
+ * | Position |   Color   |
+ * |==========|===========|
+ * | (-1, -1) | (0, 0, 0) |
+ * | (-1, +1) | (0, 1, 0) |
+ * | (+1, -1) | (1, 0, 0) |
+ *
+ * This triangle cannot cover all four samples.
+ *
+ * When default interpolation is used, the vertex color is interpolated
+ * once, most likely in the pixel center.
+ *
+ * When per-sample interpolation is used, the vertex color is interpolated
+ * several times, producing a distinct value for each covered sample.
+ * Due to the asymmetry of sample positions, the resolved pixel color must
+ * not match the color produced by default interpolation.
+ *
+ * OpenGL specs do not guarantee specific sample positions, so the test
+ * checks only that the resolved colors are different.
+ */
+function runInterpolationTest() {
+    debug("");
+    debug("Testing multisample interpolation");
+
+    function draw(program) {
+        gl.viewport(0, 0, 1, 1);
+        gl.useProgram(program);
+
+        const posLoc = gl.getAttribLocation(program, "position");
+        const buf = gl.createBuffer();
+        gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+        gl.bufferData(
+            gl.ARRAY_BUFFER,
+            new Float32Array([
+                -1.0, -1.0,
+                -1.0, +1.0,
+                +1.0, -1.0]),
+            gl.STATIC_DRAW);
+
+        gl.vertexAttribPointer(posLoc, 2, gl.FLOAT, false, 0, 0);
+        gl.enableVertexAttribArray(posLoc);
+
+        const rbo = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+        gl.renderbufferStorageMultisample(gl.RENDERBUFFER, 4, gl.RGBA8, 1, 1);
+
+        const fbo = gl.createFramebuffer();
+        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+        gl.clear(gl.COLOR_BUFFER_BIT);
+        gl.drawArrays(gl.TRIANGLES, 0, 3);
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fbo);
+        gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
+        gl.blitFramebuffer(0, 0, 1, 1, 0, 0, 1, 1, gl.COLOR_BUFFER_BIT, gl.NEAREST);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+        gl.bindFramebuffer(gl.READ_FRAMEBUFFER, null);
+    }
+
+    const vertexCenter = `#version 300 es
+        in vec4 position;
+        out vec4 interp_color;
+        void main() {
+            gl_Position = position;
+            interp_color = vec4(position.xy * 0.5 + 0.5, 0.0, 1.0);
+        }`;
+
+    const fragmentCenter = `#version 300 es
+        precision highp float;
+        in vec4 interp_color;
+        out vec4 fragColor;
+        void main() {
+            fragColor = interp_color;
+        }`;
+    const programCenter = wtu.setupProgram(gl, [vertexCenter, fragmentCenter]);
+
+    draw(programCenter);
+    const centerColor = new Uint8Array(4);
+    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, centerColor);
+
+    const vertexSample = `#version 300 es
+        #extension GL_OES_shader_multisample_interpolation : require
+        in vec4 position;
+        sample out vec4 interp_color;
+        void main() {
+            gl_Position = position;
+            interp_color = vec4(position.xy * 0.5 + 0.5, 0.0, 1.0);
+        }`;
+
+    const fragmentSample = `#version 300 es
+        #extension GL_OES_shader_multisample_interpolation : require
+        precision highp float;
+        sample in vec4 interp_color;
+        out vec4 fragColor;
+        void main() {
+            fragColor = interp_color;
+        }`;
+    const programSample = wtu.setupProgram(gl, [vertexSample, fragmentSample]);
+
+    draw(programSample);
+    const sampleColor = new Uint8Array(4);
+    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, sampleColor);
+
+    const message = `Pixel-center value: ${centerColor}, sample-average value: ${sampleColor}`;
+    if (centerColor[0] == sampleColor[0] && centerColor[1] == sampleColor[1]) {
+        testFailed(message);
+    } else {
+        testPassed(message);
+    }
+}
+
+function runTest() {
+    if (!gl) {
+        testFailed("WebGL context does not exist");
+        return;
+    }
+    testPassed("WebGL context exists");
+
+    runQueryTests(false);
+    runShaderTests(false);
+
+    debug("");
+    ext = gl.getExtension("OES_shader_multisample_interpolation");
+    wtu.runExtensionSupportedTest(gl, "OES_shader_multisample_interpolation", ext !== null);
+
+    if (!ext) {
+        testPassed("No OES_shader_multisample_interpolation support -- this is legal");
+    } else {
+        testPassed("Successfully enabled OES_shader_multisample_interpolation extension");
+        runQueryTests(true);
+        runShaderTests(true);
+        runInterpolationTest();
+    }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-blend-func-extended.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-blend-func-extended.html
new file mode 100644
index 0000000000..792e9aafa7
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-blend-func-extended.html
@@ -0,0 +1,26 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL 2.0 WEBGL_blend_func_extended Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas width="32" height="32" id="c"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+var contextVersion = 2;
+</script>
+<script src="../../js/tests/webgl-blend-func-extended.js"></script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-clip-cull-distance.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-clip-cull-distance.html
new file mode 100644
index 0000000000..cb2253c326
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-clip-cull-distance.html
@@ -0,0 +1,475 @@
+<!--
+Copyright (c) 2022 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL WEBGL_clip_cull_distance Conformance Tests</title>
+<LINK rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas width="32" height="32" id="c"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the WEBGL_clip_cull_distance extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext("c", null, 2);
+var ext;
+const w = gl.drawingBufferWidth;
+const h = gl.drawingBufferHeight;
+
+function runTestNoExtension() {
+  debug("");
+  debug("Check parameters and capabilities without the extension");
+
+  shouldBeNull("gl.getParameter(0x0D32 /* MAX_CLIP_DISTANCES_WEBGL */)");
+  wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+  shouldBeNull("gl.getParameter(0x82F9 /* MAX_CULL_DISTANCES_WEBGL */)");
+  wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+  shouldBeNull("gl.getParameter(0x82FA /* MAX_COMBINED_CLIP_AND_CULL_DISTANCES_WEBGL */)");
+  wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  const assertState = (i) => {
+    shouldBeFalse(`gl.isEnabled(${0x3000 + i} /* CLIP_DISTANCE${i}_WEBGL */)`);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+
+    shouldBeNull(`gl.getParameter(${0x3000 + i} /* CLIP_DISTANCE${i}_WEBGL */)`);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+  };
+
+  for (let i = 0; i < 8; i++) {
+    assertState(i);
+
+    gl.enable(0x3000 + i /* CLIP_DISTANCEi_WEBGL */);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "capability unknown without enabling the extension");
+
+    assertState(i);
+
+    gl.disable(0x3000 + i /* CLIP_DISTANCEi_WEBGL */);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "capability unknown without enabling the extension");
+
+    assertState(i);
+  }
+
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+  debug("");
+}
+
+function checkEnums() {
+  debug("");
+  debug("Check enums");
+  shouldBe("ext.MAX_CLIP_DISTANCES_WEBGL", "0x0D32");
+  shouldBe("ext.MAX_CULL_DISTANCES_WEBGL", "0x82F9");
+  shouldBe("ext.MAX_COMBINED_CLIP_AND_CULL_DISTANCES_WEBGL", "0x82FA");
+  shouldBe("ext.CLIP_DISTANCE0_WEBGL", "0x3000");
+  shouldBe("ext.CLIP_DISTANCE1_WEBGL", "0x3001");
+  shouldBe("ext.CLIP_DISTANCE2_WEBGL", "0x3002");
+  shouldBe("ext.CLIP_DISTANCE3_WEBGL", "0x3003");
+  shouldBe("ext.CLIP_DISTANCE4_WEBGL", "0x3004");
+  shouldBe("ext.CLIP_DISTANCE5_WEBGL", "0x3005");
+  shouldBe("ext.CLIP_DISTANCE6_WEBGL", "0x3006");
+  shouldBe("ext.CLIP_DISTANCE7_WEBGL", "0x3007");
+}
+
+function checkQueries() {
+  debug("");
+  debug("Check parameters");
+  shouldBeGreaterThanOrEqual('gl.getParameter(ext.MAX_CLIP_DISTANCES_WEBGL)', '8');
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  const maxCullDistances = gl.getParameter(ext.MAX_CULL_DISTANCES_WEBGL);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  if (maxCullDistances == 0) {
+    testPassed("No cull distance support");
+    shouldBe("gl.getParameter(ext.MAX_COMBINED_CLIP_AND_CULL_DISTANCES_WEBGL)", "0");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+  } else if (maxCullDistances >= 8) {
+    testPassed("Optional cull distance support");
+    shouldBeGreaterThanOrEqual("gl.getParameter(ext.MAX_COMBINED_CLIP_AND_CULL_DISTANCES_WEBGL)", "8");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+  } else {
+    testFailed("Invalid number of supported cull distances");
+  }
+
+  debug("");
+  debug("Check clip distance capabilities");
+
+  const assertState = (i, s) => {
+    shouldBe(`gl.isEnabled(${0x3000 + i} /* CLIP_DISTANCE${i}_WEBGL */)`, s ? "true" : "false");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+    shouldBe(`gl.getParameter(${0x3000 + i} /* CLIP_DISTANCE${i}_WEBGL */)`, s ? "true" : "false");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+  };
+
+  for (let i = 0; i < 8; i++) {
+    assertState(i, false);
+
+    gl.enable(ext.CLIP_DISTANCE0_WEBGL + i);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+    assertState(i, true);
+
+    gl.disable(ext.CLIP_DISTANCE0_WEBGL + i);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+    assertState(i, false);
+  }
+}
+
+function checkClipDistance() {
+  debug("");
+  debug("Check clip distance operation");
+
+  const vs = `#version 300 es
+#extension GL_ANGLE_clip_cull_distance : require
+
+uniform vec4 u_plane;
+in vec2 a_position;
+void main()
+{
+    gl_Position = vec4(a_position, 0.0, 1.0);
+    gl_ClipDistance[0] = dot(gl_Position, u_plane);
+}`;
+
+  const program = wtu.setupProgram(gl, [vs, wtu.simpleColorFragmentShaderESSL300]);
+  gl.useProgram(program);
+  gl.uniform4fv(gl.getUniformLocation(program, 'u_color'), [1.0, 0.0, 0.0, 1.0]);
+
+  gl.enable(ext.CLIP_DISTANCE0_WEBGL);
+
+  // Clear to blue
+  gl.clearColor(0, 0, 1, 1);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+
+  wtu.setupUnitQuad(gl);
+
+  // Draw full screen quad with color red
+  gl.uniform4f(gl.getUniformLocation(program, "u_plane"), 1, 0, 0, 0.5);
+  wtu.drawUnitQuad(gl);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  // All pixels on the left of the plane x = -0.5 must be blue
+  let x      = 0;
+  let y      = 0;
+  let width  = w / 4 - 1;
+  let height = h;
+  wtu.checkCanvasRect(gl, x, y, width, height,
+                      [0, 0, 255, 255], "should be blue");
+
+  // All pixels on the right of the plane x = -0.5 must be red
+  x      = w / 4 + 2;
+  y      = 0;
+  width  = w - x;
+  height = h;
+  wtu.checkCanvasRect(gl, x, y, width, height,
+                      [255, 0, 0, 255], "should be red");
+
+  // Clear to green
+  gl.clearColor(0, 1, 0, 1);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+
+  // Draw full screen quad with color red
+  gl.uniform4f(gl.getUniformLocation(program, "u_plane"), -1, 0, 0, -0.5);
+  wtu.drawUnitQuad(gl);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  // All pixels on the left of the plane x = -0.5 must be red
+  x      = 0;
+  y      = 0;
+  width  = w / 4 - 1;
+  height = h;
+  wtu.checkCanvasRect(gl, x, y, width, height,
+                      [255, 0, 0, 255], "should be red");
+
+  // All pixels on the right of the plane x = -0.5 must be green
+  x      = w / 4 + 2;
+  y      = 0;
+  width  = w - x;
+  height = h;
+  wtu.checkCanvasRect(gl, x, y, width, height,
+                      [0, 255, 0, 255], "should be green");
+
+  // Disable CLIP_DISTANCE0 and draw again
+  gl.disable(ext.CLIP_DISTANCE0_WEBGL);
+  wtu.drawUnitQuad(gl);
+
+  // All pixels must be red
+  wtu.checkCanvas(gl, [255, 0, 0, 255], "should be red");
+}
+
+function checkClipDistanceInterpolation() {
+  debug("");
+  debug("Check clip distance interpolation");
+
+  const vs = `#version 300 es
+#extension GL_ANGLE_clip_cull_distance : require
+in vec2 a_position;
+void main()
+{
+  gl_Position = vec4(a_position, 0.0, 1.0);
+  gl_ClipDistance[0] = dot(gl_Position, vec4( 1,  0, 0, 0.5));
+  gl_ClipDistance[1] = dot(gl_Position, vec4(-1,  0, 0, 0.5));
+  gl_ClipDistance[2] = dot(gl_Position, vec4( 0,  1, 0, 0.5));
+  gl_ClipDistance[3] = dot(gl_Position, vec4( 0, -1, 0, 0.5));
+  gl_ClipDistance[4] = gl_ClipDistance[0];
+  gl_ClipDistance[5] = gl_ClipDistance[1];
+  gl_ClipDistance[6] = gl_ClipDistance[2];
+  gl_ClipDistance[7] = gl_ClipDistance[3];
+}`;
+
+  const fs = `#version 300 es
+#extension GL_ANGLE_clip_cull_distance : require
+precision highp float;
+out vec4 my_FragColor;
+void main()
+{
+  float r = gl_ClipDistance[0] + gl_ClipDistance[1];
+  float g = gl_ClipDistance[2] + gl_ClipDistance[3];
+  float b = gl_ClipDistance[4] + gl_ClipDistance[5];
+  float a = gl_ClipDistance[6] + gl_ClipDistance[7];
+  my_FragColor = vec4(r, g, b, a) * 0.5;
+}`;
+
+  const program = wtu.setupProgram(gl, [vs, fs]);
+  gl.useProgram(program);
+
+  gl.enable(ext.CLIP_DISTANCE0_WEBGL);
+  gl.enable(ext.CLIP_DISTANCE1_WEBGL);
+  gl.enable(ext.CLIP_DISTANCE2_WEBGL);
+  gl.enable(ext.CLIP_DISTANCE3_WEBGL);
+  gl.enable(ext.CLIP_DISTANCE4_WEBGL);
+  gl.enable(ext.CLIP_DISTANCE5_WEBGL);
+  gl.enable(ext.CLIP_DISTANCE6_WEBGL);
+  gl.enable(ext.CLIP_DISTANCE7_WEBGL);
+
+  wtu.setupUnitQuad(gl);
+
+  // Clear to blue
+  gl.clearColor(0, 0, 1, 1);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+
+  // Draw full screen quad with color gray
+  wtu.drawUnitQuad(gl);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  const data = new Uint8Array(w * h * 4);
+  gl.readPixels(0, 0, w, h, gl.RGBA, gl.UNSIGNED_BYTE, data);
+  let passed = true;
+  for (let x = 0; x < w; x++) {
+    for (let y = 0; y < h; y++) {
+      const currentPosition = (y * h + x) * 4;
+      const inside = (x >= w / 4 && x < w * 3 / 4 && y >= h / 4 && y < h * 3 / 4);
+      const expected = inside ? [127, 127, 127, 127] : [0, 0, 255, 255];
+      const actual = data.slice(currentPosition, currentPosition + 4);
+      if (Math.abs(actual[0] - expected[0]) > 1 ||
+          Math.abs(actual[1] - expected[1]) > 1 ||
+          Math.abs(actual[2] - expected[2]) > 1 ||
+          Math.abs(actual[3] - expected[3]) > 1) {
+        passed = false;
+      }
+    }
+  }
+  if (passed) {
+    testPassed("Correct clip distance interpolation");
+  } else {
+    testFailed("Incorrect clip distance interpolation");
+  }
+}
+
+function checkCullDistance() {
+  debug("");
+  debug("Check cull distance operation");
+
+  if (gl.getParameter(ext.MAX_CULL_DISTANCES_WEBGL) == 0) {
+    testPassed("No cull distance support");
+    return;
+  }
+
+  const vs = `#version 300 es
+#extension GL_ANGLE_clip_cull_distance : require
+
+uniform vec4 u_plane;
+in vec2 a_position;
+void main()
+{
+    gl_Position = vec4(a_position, 0.0, 1.0);
+    gl_CullDistance[0] = dot(gl_Position, u_plane);
+}`;
+
+  const program = wtu.setupProgram(gl, [vs, wtu.simpleColorFragmentShaderESSL300]);
+  gl.useProgram(program);
+  gl.uniform4fv(gl.getUniformLocation(program, 'u_color'), [1.0, 0.0, 0.0, 1.0]);
+
+  // Clear to blue
+  gl.clearColor(0, 0, 1, 1);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+
+  wtu.setupUnitQuad(gl);
+
+  // Draw full screen quad with color red
+  gl.uniform4f(gl.getUniformLocation(program, "u_plane"), 1, 0, 0, 0.5);
+  wtu.drawUnitQuad(gl);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  // All pixels must be red
+  wtu.checkCanvas(gl, [255, 0, 0, 255], "should be red");
+
+  // Clear to green
+  gl.clearColor(0, 1, 0, 1);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+
+  // Draw full screen quad with color red
+  gl.uniform4f(gl.getUniformLocation(program, "u_plane"), -1, 1, 0, -0.5);
+  wtu.drawUnitQuad(gl);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  // All pixels above the y > x line must be red
+  const data = new Uint8Array(w * h * 4);
+  gl.readPixels(0, 0, w, h, gl.RGBA, gl.UNSIGNED_BYTE, data);
+  let passed = true;
+  for (let x = 0; x < w; ++x) {
+    for (let y = 0; y < h; ++y) {
+      if (y <= x + 2 && y >= x - 2) continue; // skip the edge
+      const currentPosition = (y * h + x) * 4;
+      const actual = data.slice(currentPosition, currentPosition + 2);
+      const expected = (y > x) ? [255, 0] : [0, 255];
+      if (actual[0] != expected[0] || actual[1] != expected[1]) {
+        passed = false;
+      }
+    }
+  }
+  if (passed) {
+    testPassed("Correct cull distance operation");
+  } else {
+    testFailed("Incorrect cull distance operation");
+  }
+}
+
+function checkCullDistanceInterpolation() {
+  debug("");
+  debug("Check cull distance interpolation");
+
+  if (gl.getParameter(ext.MAX_CULL_DISTANCES_WEBGL) == 0) {
+    testPassed("No cull distance support");
+    return;
+  }
+
+  const vs = `#version 300 es
+#extension GL_ANGLE_clip_cull_distance : require
+in vec2 a_position;
+void main()
+{
+  gl_Position = vec4(a_position, 0.0, 1.0);
+  gl_CullDistance[0] = dot(gl_Position, vec4( 1,  0, 0, 1));
+  gl_CullDistance[1] = dot(gl_Position, vec4(-1,  0, 0, 1));
+  gl_CullDistance[2] = dot(gl_Position, vec4( 0,  1, 0, 1));
+  gl_CullDistance[3] = dot(gl_Position, vec4( 0, -1, 0, 1));
+  gl_CullDistance[4] = gl_CullDistance[0];
+  gl_CullDistance[5] = gl_CullDistance[1];
+  gl_CullDistance[6] = gl_CullDistance[2];
+  gl_CullDistance[7] = gl_CullDistance[3];
+}`;
+
+  const fs = `#version 300 es
+#extension GL_ANGLE_clip_cull_distance : require
+precision highp float;
+out vec4 my_FragColor;
+void main()
+{
+  float r = gl_CullDistance[0] + gl_CullDistance[1];
+  float g = gl_CullDistance[2] + gl_CullDistance[3];
+  float b = gl_CullDistance[4] + gl_CullDistance[5];
+  float a = gl_CullDistance[6] + gl_CullDistance[7];
+  my_FragColor = vec4(r, g, b, a) * 0.25;
+}`;
+
+  const program = wtu.setupProgram(gl, [vs, fs]);
+  gl.useProgram(program);
+
+  // Clear to blue
+  gl.clearColor(0, 0, 1, 1);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+
+  wtu.setupQuad(gl, {scale: 0.5});
+
+  // Draw a small quad with color gray
+  wtu.drawUnitQuad(gl);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+  const data = new Uint8Array(w * h * 4);
+  gl.readPixels(0, 0, w, h, gl.RGBA, gl.UNSIGNED_BYTE, data);
+  let passed = true;
+  for (let x = 0; x < w; x++) {
+    for (let y = 0; y < h; y++) {
+      const currentPosition = (y * h + x) * 4;
+      const inside = (x >= w / 4 && x < w * 3 / 4 && y >= h / 4 && y < h * 3 / 4);
+      const expected = inside ? [127, 127, 127, 127] : [0, 0, 255, 255];
+      const actual = data.slice(currentPosition, currentPosition + 4);
+      if (Math.abs(actual[0] - expected[0]) > 1 ||
+          Math.abs(actual[1] - expected[1]) > 1 ||
+          Math.abs(actual[2] - expected[2]) > 1 ||
+          Math.abs(actual[3] - expected[3]) > 1) {
+        passed = false;
+      }
+    }
+  }
+  if (passed) {
+    testPassed("Correct cull distance interpolation");
+  } else {
+    testFailed("Incorrect cull distance interpolation");
+  }
+}
+
+function runTestExtension() {
+  checkEnums();
+  checkQueries();
+
+  checkClipDistance();
+  checkClipDistanceInterpolation();
+
+  checkCullDistance();
+  checkCullDistanceInterpolation();
+}
+
+function runTest() {
+  if (!gl) {
+    testFailed("context does not exist");
+  } else {
+    testPassed("context exists");
+
+    runTestNoExtension();
+
+    ext = gl.getExtension("WEBGL_clip_cull_distance");
+
+    wtu.runExtensionSupportedTest(gl, "WEBGL_clip_cull_distance", ext !== null);
+
+    if (ext !== null) {
+      runTestExtension();
+    } else {
+      testPassed("No WEBGL_clip_cull_distance support -- this is legal");
+    }
+  }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-provoking-vertex.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-provoking-vertex.html
new file mode 100644
index 0000000000..3737409b3a
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-provoking-vertex.html
@@ -0,0 +1,165 @@
+<!--
+Copyright (c) 2022 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL WEBGL_provoking_vertex Conformance Tests</title>
+<LINK rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas width="16" height="16" id="c"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the WEBGL_provoking_vertex extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext("c", null, 2);
+var ext;
+
+function runTestNoExtension() {
+    debug("");
+    debug("Check getParameter without the extension");
+    shouldBeNull("gl.getParameter(0x8E4F /* PROVOKING_VERTEX_WEBGL */)");
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+    debug("");
+}
+
+function runTestExtension() {
+    debug("");
+    debug("Check enums");
+    shouldBe("ext.FIRST_VERTEX_CONVENTION_WEBGL", "0x8E4D");
+    shouldBe("ext.LAST_VERTEX_CONVENTION_WEBGL", "0x8E4E");
+    shouldBe("ext.PROVOKING_VERTEX_WEBGL", "0x8E4F");
+
+    debug("");
+    debug("Check default state");
+    shouldBe("gl.getParameter(ext.PROVOKING_VERTEX_WEBGL)", "ext.LAST_VERTEX_CONVENTION_WEBGL");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "parameter known with the extension enabled");
+
+    debug("");
+    debug("Check state updates");
+    ext.provokingVertexWEBGL(ext.FIRST_VERTEX_CONVENTION_WEBGL);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "provokingVertexWEBGL(ext.FIRST_VERTEX_CONVENTION_WEBGL) generates no errors");
+    shouldBe("gl.getParameter(ext.PROVOKING_VERTEX_WEBGL)", "ext.FIRST_VERTEX_CONVENTION_WEBGL");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+    ext.provokingVertexWEBGL(ext.LAST_VERTEX_CONVENTION_WEBGL);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "provokingVertexWEBGL(ext.LAST_VERTEX_CONVENTION_WEBGL) generates no errors");
+    shouldBe("gl.getParameter(ext.PROVOKING_VERTEX_WEBGL)", "ext.LAST_VERTEX_CONVENTION_WEBGL");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+    debug("");
+    debug("Check invalid provoking vertex mode");
+    ext.provokingVertexWEBGL(ext.FIRST_VERTEX_CONVENTION_WEBGL);
+    ext.provokingVertexWEBGL(ext.PROVOKING_VERTEX_WEBGL);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "invalid provoking mode generates an error");
+    shouldBe("gl.getParameter(ext.PROVOKING_VERTEX_WEBGL)", "ext.FIRST_VERTEX_CONVENTION_WEBGL");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+    debug("");
+    debug("Check provoking vertex operation");
+
+    const vs = `#version 300 es
+      in int intAttrib;
+      in vec2 position;
+      flat out int attrib;
+      void main() {
+        gl_Position = vec4(position, 0, 1);
+        attrib = intAttrib;
+      }`;
+
+    const fs = `#version 300 es
+      flat in int attrib;
+      out int fragColor;
+      void main() {
+        fragColor = attrib;
+      }`;
+
+    const program = wtu.setupProgram(gl, [vs, fs]);
+    gl.useProgram(program);
+
+    const tex = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, tex);
+    gl.texStorage2D(gl.TEXTURE_2D, 1, gl.R32I, 16, 16);
+
+    const fb = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
+
+    const vb = gl.createBuffer();
+    gl.bindBuffer(gl.ARRAY_BUFFER, vb);
+    const buf = new ArrayBuffer(36);
+    new Float32Array(buf, 0, 6).set([-1.0, -1.0, 3.0, -1.0, -1.0, 3.0]);
+    new Int32Array(buf, 24, 3).set([1, 2, 3]);
+    gl.bufferData(gl.ARRAY_BUFFER, buf, gl.STATIC_DRAW);
+
+    const positionLocation = gl.getAttribLocation(program, "position");
+    gl.enableVertexAttribArray(positionLocation);
+    gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
+
+    const intAttribLocation = gl.getAttribLocation(program, "intAttrib");
+    gl.enableVertexAttribArray(intAttribLocation);
+    gl.vertexAttribIPointer(intAttribLocation, 1, gl.INT, 0, 24);
+
+    const pixel = new Int32Array(4);
+
+    ext.provokingVertexWEBGL(ext.LAST_VERTEX_CONVENTION_WEBGL);
+    gl.clearBufferiv(gl.COLOR, 0, new Int32Array(4));
+    gl.drawArrays(gl.TRIANGLES, 0, 3);
+    gl.readPixels(0, 0, 1, 1, gl.RGBA_INTEGER, gl.INT, pixel);
+
+    if (pixel[0] == 3) {
+        testPassed("Correct last provoking vertex");
+    } else {
+        testFailed("Incorrect last provoking vertex");
+    }
+
+    ext.provokingVertexWEBGL(ext.FIRST_VERTEX_CONVENTION_WEBGL);
+    gl.clearBufferiv(gl.COLOR, 0, new Int32Array(4));
+    gl.drawArrays(gl.TRIANGLES, 0, 3);
+    gl.readPixels(0, 0, 1, 1, gl.RGBA_INTEGER, gl.INT, pixel);
+
+    if (pixel[0] == 1) {
+        testPassed("Correct first provoking vertex");
+    } else {
+        testFailed("Incorrect first provoking vertex");
+    }
+}
+
+function runTest() {
+  if (!gl) {
+    testFailed("context does not exist");
+  } else {
+    testPassed("context exists");
+
+    runTestNoExtension();
+
+    ext = gl.getExtension("WEBGL_provoking_vertex");
+
+    wtu.runExtensionSupportedTest(gl, "WEBGL_provoking_vertex", ext !== null);
+
+    if (ext !== null) {
+      runTestExtension();
+    } else {
+      testPassed("No WEBGL_provoking_vertex support -- this is legal");
+    }
+  }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-render-shared-exponent.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-render-shared-exponent.html
new file mode 100644
index 0000000000..11d505fcc6
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-render-shared-exponent.html
@@ -0,0 +1,251 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL WEBGL_render_shared_exponent Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the WEBGL_render_shared_exponent extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext(null, null, 2);
+var ext;
+const color = [64.0, 32.0, 16.0, 1.0];
+
+function drawTest() {
+    wtu.clearAndDrawUnitQuad(gl);
+
+    wtu.checkCanvasRect(gl, 0, 0, 1, 1, color,
+                        "reading with the RGBA format and FLOAT type", 1,
+                        new Float32Array(4), gl.FLOAT, gl.RGBA);
+
+    const implementationType = gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_TYPE);
+    const implementationFormat = gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_FORMAT);
+    if (implementationFormat == gl.RGB && implementationType == gl.UNSIGNED_INT_5_9_9_9_REV) {
+        // Shared exponent value may be implementation
+        // specific, so compare decoded values.
+        const value = new Uint32Array(1);
+        gl.readPixels(0, 0, 1, 1, gl.RGB, gl.UNSIGNED_INT_5_9_9_9_REV, value);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+        let r = (value >>  0) & 0x1FF;
+        let g = (value >>  9) & 0x1FF;
+        let b = (value >> 18) & 0x1FF;
+        let e = (value >> 27) & 0x01F;
+        debug(`Raw value: 0x${value[0].toString(16).toUpperCase()}, ` +
+              `Raw components: R = ${r}, G = ${g}, B = ${b}, E = ${e}`);
+
+        e = Math.pow(2, e - 24);
+        r *= e;
+        g *= e;
+        b *= e;
+        debug(`Decoded color: (${r}, ${g}, ${b})`);
+
+        if (r == color[0] && g == color[1] && b == color[2]) {
+            testPassed("reading with the exact format/type");
+        } else {
+            testFailed("reading with the exact format/type");
+        }
+    }
+}
+
+function renderbufferTest(isSupported) {
+    debug("");
+    debug(`RGB9_E5 renderbuffer: ` +
+          `${!isSupported ? "NOT " : ""}supported`);
+
+    const rbo = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+    gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGB9_E5, 1, 1);
+    if (!isSupported) {
+        wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "renderbuffer allocation failed");
+        return;
+    }
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "renderbuffer allocation succeeded");
+
+    const fbo = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+    wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+    drawTest();
+}
+
+function textureTest(isRenderable) {
+    debug("");
+    debug(`RGB9_E5 texture: ` +
+          `${!isRenderable ? "NOT " : ""}renderable`);
+
+    const tex = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, tex);
+    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB9_E5, 1, 1, 0, gl.RGB, gl.UNSIGNED_INT_5_9_9_9_REV, null);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "texture allocation succeeded");
+
+    const fbo = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
+
+    if (!isRenderable) {
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_INCOMPLETE_ATTACHMENT);
+        return;
+    }
+    wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+    drawTest();
+}
+
+function formatTest(isEnabled) {
+    const program = wtu.setupProgram(gl, [wtu.simpleVertexShader,
+                                          wtu.simpleColorFragmentShader]);
+    gl.useProgram(program);
+    gl.uniform4fv(gl.getUniformLocation(program, "u_color"), color);
+
+    wtu.setupUnitQuad(gl);
+
+    renderbufferTest(isEnabled);
+    textureTest(isEnabled);
+}
+
+function colorMaskTest() {
+    debug("");
+    debug("Test color write masks with shared exponent color buffers");
+
+    const fs = `#version 300 es
+        precision highp float;
+        layout(location = 0) out vec4 color0;
+        layout(location = 1) out vec4 color1;
+        void main() {
+            color0 = vec4(1.0, 0.0, 0.0, 1.0);
+            color1 = vec4(0.0, 1.0, 0.0, 1.0);
+        }`;
+    const program = wtu.setupProgram(gl, [wtu.simpleVertexShaderESSL300, fs]);
+    gl.useProgram(program);
+
+    const fbo = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+
+    const rb0 = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, rb0);
+    gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGB9_E5, 4, 4);
+    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rb0);
+
+    const rb1 = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, rb1);
+    gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA8, 4, 4);
+    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT1, gl.RENDERBUFFER, rb1);
+
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+    wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+    const clearValue = new Float32Array(4);
+    const dbiExt = gl.getExtension("OES_draw_buffers_indexed");
+
+    function expectError(enabled, effectiveMask, operation) {
+        if (!enabled ||
+            effectiveMask == 0x0 /* 0000 */ ||
+            effectiveMask == 0x8 /* 000A */ ||
+            effectiveMask == 0x7 /* RGB0 */ ||
+            effectiveMask == 0xF /* RGBA */ ) {
+            wtu.glErrorShouldBe(gl, gl.NO_ERROR, operation);
+        } else {
+            wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, operation);
+        }
+    }
+
+    function runOps(enabled, mask0) {
+        wtu.drawUnitQuad(gl);
+        expectError(enabled, mask0, "draw");
+
+        gl.clear(gl.COLOR_BUFFER_BIT);
+        expectError(enabled, mask0, "clear");
+
+        gl.clearBufferfv(gl.COLOR, 0, clearValue);
+        expectError(enabled, mask0, "clearBufferfv(RGB9_E5)");
+        gl.clearBufferfv(gl.COLOR, 1, clearValue);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "clearBufferfv(RGBA8)");
+    }
+
+    for (let mask = 0; mask < 16; mask++) {
+        for (const enabled of [false, true]) {
+            debug("");
+            debug(`Setting common color mask ` +
+                  `${mask & 1 ? "R" : "0"}` +
+                  `${mask & 2 ? "G" : "0"}` +
+                  `${mask & 4 ? "B" : "0"}` +
+                  `${mask & 8 ? "A" : "0"}` +
+                  " with RGB9_E5 attachment " +
+                  (enabled ? "enabled" : "disabled"));
+            gl.colorMask(mask & 1, mask & 2, mask & 4, mask & 8);
+            gl.drawBuffers([enabled ? gl.COLOR_ATTACHMENT0 : gl.NONE,
+                            gl.COLOR_ATTACHMENT1]);
+
+            runOps(enabled, mask);
+
+            if (dbiExt) {
+                debug("Setting incompatible color mask on unused draw buffer")
+                dbiExt.colorMaskiOES(2, true, false, false, false);
+                runOps(enabled, mask); // common mask remains on draw buffer 0
+
+                debug("Setting incompatible color mask on RGBA8 draw buffer")
+                dbiExt.colorMaskiOES(1, true, false, false, false);
+                runOps(enabled, mask); // common mask remains on draw buffer 0
+
+                debug("Setting incompatible color mask on RGB9_E5 draw buffer")
+                dbiExt.colorMaskiOES(0, true, false, false, false);
+                runOps(enabled, 1); // overridden
+
+                debug("Setting compatible color mask on RGB9_E5 draw buffer")
+                dbiExt.colorMaskiOES(0, true, true, true, false);
+                runOps(enabled, 7); // overridden
+            }
+        }
+    }
+}
+
+function runTest() {
+    if (!gl) {
+        testFailed("context does not exist");
+        return;
+    }
+    testPassed("context exists");
+
+    debug("");
+    debug("Testing shared exponent rendering with extension disabled");
+    formatTest(false);
+
+    ext = gl.getExtension("WEBGL_render_shared_exponent");
+    wtu.runExtensionSupportedTest(gl, "WEBGL_render_shared_exponent", ext !== null);
+
+    if (ext !== null) {
+        debug("");
+        debug("Testing shared exponent rendering with extension enabled");
+        formatTest(true);
+        colorMaskTest();
+    } else {
+        testPassed("No WEBGL_render_shared_exponent support -- this is legal");
+    }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-shader-pixel-local-storage.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-shader-pixel-local-storage.html
new file mode 100644
index 0000000000..e548eea46c
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-shader-pixel-local-storage.html
@@ -0,0 +1,445 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL WEBGL_shader_pixel_local_storage Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/desktop-gl-constants.js"></script>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+<script src="../../js/tests/compositing-test.js"></script>
+<script src="../../js/tests/invalid-vertex-attrib-test.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<canvas id="canvas" width="128" height="128" style="background-color:#080"> </canvas>
+<canvas id="canvas_no_alpha" width="128" height="128"> </canvas>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the WEBGL_shader_pixel_local_storage " +
+            "extension, if it is available.");
+
+const wtu = WebGLTestUtils;
+const canvas = document.getElementById("canvas");
+const gl = wtu.create3DContext(canvas, {alpha: true}, 2);
+const gl_no_alpha = wtu.create3DContext("canvas_no_alpha", {alpha: false}, 2);
+let pls = null;
+
+// Outputs a fullscreen quad from a 4-vertex triangle strip.
+const fullscreenQuadVertexShader = `#version 300 es
+void main() {
+    gl_Position.x = (gl_VertexID & 1) == 0 ? -1. : 1.;
+    gl_Position.y = (gl_VertexID & 2) == 0 ? -1. : 1.;
+    gl_Position.zw = vec2(0, 1);
+}`;
+
+function arraysEqual(a, b) {
+  if (typeof a !== typeof b)
+    return false;
+  if (a.length != b.length)
+    return false;
+  for (let i = 0; i < a.length; ++i) {
+    if (a[i] !== b[i])
+      return false;
+  }
+  return true;
+}
+
+async function runTest() {
+  if (!gl) {
+    testFailed("WebGL2 context does not exist");
+    finishTest();
+    return;
+  }
+
+  debug("\nCheck the behavior surrounding WEBGL_shader_pixel_local_storage being enabled.");
+  checkExtensionNotSupportedWhenDisabled();
+  checkDependencyExtensionsEnabled(false);
+  debug("Enable WEBGL_shader_pixel_local_storage.");
+  pls = gl.getExtension("WEBGL_shader_pixel_local_storage");
+  wtu.runExtensionSupportedTest(gl, "WEBGL_shader_pixel_local_storage", pls != null);
+  if (!pls) {
+    finishTest();
+    return;
+  }
+  checkDependencyExtensionsEnabled(true);
+
+  checkImplementationDependentLimits();
+  checkInitialValues();
+  checkWebGLNonNormativeBehavior();
+
+  await checkRendering(gl);
+  await checkRendering(gl_no_alpha);
+
+  finishTest();
+}
+
+function checkExtensionNotSupportedWhenDisabled() {
+  debug("\nCheck that a context does not support WEBGL_shader_pixel_local_storage before it is " +
+        "enabled");
+  shouldBeNull("gl.getParameter(0x96E0 /*MAX_PIXEL_LOCAL_STORAGE_PLANES_WEBGL*/)");
+  wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+  shouldBeNull(
+    "gl.getParameter(0x96E1 /*MAX_COLOR_ATTACHMENTS_WITH_ACTIVE_PIXEL_LOCAL_STORAGE_WEBGL*/)");
+  wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+  shouldBeNull(
+    "gl.getParameter(0x96E2 /*MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES_WEBGL*/)");
+  wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+  shouldBeNull(
+    "gl.getParameter(0x96E3 /*PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL*/)");
+  wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+  wtu.glErrorShouldBe(gl, gl.NONE);
+}
+
+function checkDependencyExtensionsEnabled(enabled) {
+  debug("\nCheck that dependency extensions of WEBGL_shader_pixel_local_storage are " +
+        (enabled ? "enabled" : "disabled"));
+  if (wtu.getSupportedExtensionWithKnownPrefixes(gl, "OES_draw_buffers_indexed") !== undefined) {
+    gl.getIndexedParameter(gl.BLEND_EQUATION_RGB, 1);
+    wtu.glErrorShouldBe(gl, enabled ? gl.NONE : gl.INVALID_ENUM,
+                        "OES_draw_buffers_indexed not enabled or disabled as expected");
+  }
+  if (wtu.getSupportedExtensionWithKnownPrefixes(gl, "EXT_color_buffer_float") !== undefined) {
+    gl.bindRenderbuffer(gl.RENDERBUFFER, gl.createRenderbuffer());
+    gl.renderbufferStorage(gl.RENDERBUFFER, gl.R32F, 1, 1);
+    wtu.glErrorShouldBe(gl, enabled ? gl.NONE : gl.INVALID_ENUM,
+                        "EXT_color_buffer_float not enabled or disabled as expected");
+    gl.bindRenderbuffer(gl.RENDERBUFFER, null);
+  }
+  if (wtu.getSupportedExtensionWithKnownPrefixes(gl, "EXT_color_buffer_half_float") !== undefined) {
+    gl.bindRenderbuffer(gl.RENDERBUFFER, gl.createRenderbuffer());
+    gl.renderbufferStorage(gl.RENDERBUFFER, gl.RG16F, 1, 1);
+    wtu.glErrorShouldBe(gl, enabled ? gl.NONE : gl.INVALID_ENUM,
+                        "EXT_color_buffer_half_float not enabled or disabled as expected");
+    gl.bindRenderbuffer(gl.RENDERBUFFER, null);
+  }
+}
+
+function checkImplementationDependentLimits() {
+  debug("\nVerify conformant implementation-dependent PLS limits.");
+  window.MAX_PIXEL_LOCAL_STORAGE_PLANES =
+    gl.getParameter(pls.MAX_PIXEL_LOCAL_STORAGE_PLANES_WEBGL);
+  window.MAX_COLOR_ATTACHMENTS_WITH_ACTIVE_PIXEL_LOCAL_STORAGE =
+    gl.getParameter(pls.MAX_COLOR_ATTACHMENTS_WITH_ACTIVE_PIXEL_LOCAL_STORAGE_WEBGL);
+  window.MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES =
+    gl.getParameter(pls.MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES_WEBGL);
+  wtu.glErrorShouldBe(gl, gl.NONE, "Pixel local storage queries should be supported.");
+
+  window.MAX_COLOR_ATTACHMENTS = gl.getParameter(gl.MAX_COLOR_ATTACHMENTS);
+  window.MAX_DRAW_BUFFERS = gl.getParameter(gl.MAX_DRAW_BUFFERS);
+
+  // Table 6.X: Impementation Dependent Pixel Local Storage Limits.
+  shouldBeTrue("MAX_PIXEL_LOCAL_STORAGE_PLANES >= 4");
+  shouldBeTrue("MAX_COLOR_ATTACHMENTS_WITH_ACTIVE_PIXEL_LOCAL_STORAGE >= 0");
+  shouldBeTrue("MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES >= 4");
+
+  // Logical deductions based on 6.X.
+  shouldBeTrue(`MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES >=
+               MAX_PIXEL_LOCAL_STORAGE_PLANES`);
+  shouldBeTrue(`MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES >=
+               MAX_COLOR_ATTACHMENTS_WITH_ACTIVE_PIXEL_LOCAL_STORAGE`);
+  shouldBeTrue(`MAX_COLOR_ATTACHMENTS + MAX_PIXEL_LOCAL_STORAGE_PLANES >=
+               MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES`);
+  shouldBeTrue(`MAX_DRAW_BUFFERS + MAX_PIXEL_LOCAL_STORAGE_PLANES >=
+               MAX_COMBINED_DRAW_BUFFERS_AND_PIXEL_LOCAL_STORAGE_PLANES`);
+}
+
+function checkInitialValues() {
+  debug("\nCheck that PLS state has the correct initial values.");
+  shouldBeTrue("gl.getParameter(pls.PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL) == 0");
+  wtu.glErrorShouldBe(
+      gl, gl.NONE,
+      "It's valid to query GL_PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL even when fbo 0 is bound.");
+
+  // Table 6.Y: Pixel Local Storage State
+  gl.bindFramebuffer(gl.FRAMEBUFFER, gl.createFramebuffer());
+  shouldBeTrue("gl.getParameter(pls.PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL) == 0");
+  debug("Check the initial clear values for each plane.");
+  const MAX_PIXEL_LOCAL_STORAGE_PLANES =
+    gl.getParameter(pls.MAX_PIXEL_LOCAL_STORAGE_PLANES_WEBGL);
+  for (let i = 0; i < MAX_PIXEL_LOCAL_STORAGE_PLANES; ++i)
+  {
+    expectTrue(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+        i, pls.PIXEL_LOCAL_FORMAT_WEBGL) == gl.NONE);
+    expectTrue(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+        i, pls.PIXEL_LOCAL_TEXTURE_NAME_WEBGL) == null);
+    expectTrue(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+        i, pls.PIXEL_LOCAL_TEXTURE_LEVEL_WEBGL) == 0);
+    expectTrue(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+        i, pls.PIXEL_LOCAL_TEXTURE_LAYER_WEBGL) == 0);
+    expectTrue(arraysEqual(
+        pls.getFramebufferPixelLocalStorageParameterWEBGL(
+            i, pls.PIXEL_LOCAL_CLEAR_VALUE_FLOAT_WEBGL),
+        new Float32Array([0, 0, 0, 0])));
+    expectTrue(arraysEqual(
+        pls.getFramebufferPixelLocalStorageParameterWEBGL(
+            i, pls.PIXEL_LOCAL_CLEAR_VALUE_INT_WEBGL),
+        new Int32Array([0, 0, 0, 0])));
+    expectTrue(arraysEqual(
+        pls.getFramebufferPixelLocalStorageParameterWEBGL(
+            i, pls.PIXEL_LOCAL_CLEAR_VALUE_UNSIGNED_INT_WEBGL),
+        new Uint32Array([0, 0, 0, 0])));
+  }
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+}
+
+function checkWebGLNonNormativeBehavior() {
+  debug("\nCheck the WebGL-specific behavior not found in the " +
+        "ANGLE_shader_pixel_local_storage specification.");
+  gl.bindFramebuffer(gl.FRAMEBUFFER, gl.createFramebuffer());
+
+  debug("If 'texture' has been deleted, generates an INVALID_OPERATION error.");
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  const tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  gl.texStorage2D(gl.TEXTURE_2D, 1, gl.RGBA8, 1, 1);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  gl.deleteTexture(tex);
+  pls.framebufferTexturePixelLocalStorageWEBGL(0, tex, 0, 0);
+  wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
+
+  debug("\nIf 'texture' was generated by a different WebGL2RenderingContext than this one, " +
+        "generates an INVALID_OPERATION error.");
+  const gl2 = wtu.create3DContext(null, null, 2);
+  const tex2 = gl2.createTexture();
+  gl2.bindTexture(gl2.TEXTURE_2D, tex2);
+  gl2.texStorage2D(gl2.TEXTURE_2D, 1, gl2.RGBA8, 1, 1);
+  pls.framebufferTexturePixelLocalStorageWEBGL(0, tex2, 0, 0);
+  wtu.glErrorShouldBe(gl2, gl2.NONE);
+  wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
+
+  debug("\nIf value has less than srcOffset + 4 elements, generates an INVALID_VALUE error.");
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  pls.framebufferPixelLocalClearValuefvWEBGL(0, new Float32Array(3));
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValuefvWEBGL(1, [0, 0, 0]);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueivWEBGL(2, new Int32Array(3));
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueivWEBGL(3, [0, 0, 0]);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueuivWEBGL(4, new Uint32Array(3));
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueuivWEBGL(3, [0, 0, 0]);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValuefvWEBGL(2, new Float32Array(5), 2);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValuefvWEBGL(1, [0, 0, 0, 0, 0], 2);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueivWEBGL(0, new Int32Array(5), 2);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueivWEBGL(1, [0, 0, 0, 0, 0], 2);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueuivWEBGL(2, new Uint32Array(5), 2);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+  pls.framebufferPixelLocalClearValueuivWEBGL(3, [0, 0, 0, 0, 0], 2);
+  wtu.glErrorShouldBe(gl, gl.INVALID_VALUE);
+
+  debug("\nCheck that srcOffset works properly.");
+  const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
+  pls.framebufferPixelLocalClearValuefvWEBGL(0, new Float32Array(arr), 1);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  shouldBeTrue(`arraysEqual(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                                0, pls.PIXEL_LOCAL_CLEAR_VALUE_FLOAT_WEBGL),
+                            new Float32Array([1, 2, 3, 4]))`);
+  pls.framebufferPixelLocalClearValuefvWEBGL(1, arr, 2);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  shouldBeTrue(`arraysEqual(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                                1, pls.PIXEL_LOCAL_CLEAR_VALUE_FLOAT_WEBGL),
+                            [2, 3, 4, 5])`);
+  pls.framebufferPixelLocalClearValueivWEBGL(2, new Int32Array(arr), 3);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  shouldBeTrue(`arraysEqual(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                                2, pls.PIXEL_LOCAL_CLEAR_VALUE_INT_WEBGL),
+                            new Float32Array([3, 4, 5, 6]))`);
+  pls.framebufferPixelLocalClearValueivWEBGL(3, arr, 4);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  shouldBeTrue(`arraysEqual(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                                3, pls.PIXEL_LOCAL_CLEAR_VALUE_INT_WEBGL),
+                            [4, 5, 6, 7])`);
+  pls.framebufferPixelLocalClearValueuivWEBGL(2, new Uint32Array(arr), 5);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  shouldBeTrue(`arraysEqual(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                                2, pls.PIXEL_LOCAL_CLEAR_VALUE_UNSIGNED_INT_WEBGL),
+                            new Uint32Array([5, 6, 7, 8]))`);
+  pls.framebufferPixelLocalClearValueuivWEBGL(1, arr, 6);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  shouldBeTrue(`arraysEqual(pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                                1, pls.PIXEL_LOCAL_CLEAR_VALUE_UNSIGNED_INT_WEBGL),
+                            [6, 7, 8, 9])`);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+
+  debug("\nCheck that PIXEL_LOCAL_TEXTURE_NAME_WEBGL returns a WebGLTexture.");
+  shouldBeTrue(`pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                    0, pls.PIXEL_LOCAL_TEXTURE_NAME_WEBGL) === null`);
+  window.validTex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, validTex);
+  gl.texStorage2D(gl.TEXTURE_2D, 1, gl.RGBA8, 1, 1);
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  pls.framebufferTexturePixelLocalStorageWEBGL(0, validTex, 0, 0);
+  shouldBeTrue(`pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                    0, pls.PIXEL_LOCAL_TEXTURE_NAME_WEBGL) === validTex`);
+  pls.framebufferTexturePixelLocalStorageWEBGL(0, null, 0, 0);
+  shouldBeTrue(`pls.getFramebufferPixelLocalStorageParameterWEBGL(
+                    0, pls.PIXEL_LOCAL_TEXTURE_NAME_WEBGL) === null`);
+
+  wtu.glErrorShouldBe(gl, gl.NONE);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+}
+
+async function checkRendering(localGL) {
+  const localCanvas = localGL.canvas;
+  const alpha = localGL.getContextAttributes().alpha;
+  debug("\nCheck very simple rendering with {alpha: " + alpha + "}");
+
+  const localPLS = localGL.getExtension("WEBGL_shader_pixel_local_storage");
+  if (!localPLS) {
+    testFailed("localGL doesn't support pixel local storage.");
+    return;
+  }
+
+  const tex = localGL.createTexture();
+  localGL.bindTexture(localGL.TEXTURE_2D, tex);
+  localGL.texStorage2D(localGL.TEXTURE_2D, 1, localGL.RGBA8, localCanvas.width, localCanvas.height);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+
+  const plsFBO = localGL.createFramebuffer();
+  localGL.bindFramebuffer(localGL.FRAMEBUFFER, plsFBO);
+  localPLS.framebufferTexturePixelLocalStorageWEBGL(0, tex, 0, 0);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+
+  localGL.viewport(0, 0, localCanvas.width, localCanvas.height);
+
+  // Adds a uniform color into the existing color in pixel local storage.
+  const fs = `#version 300 es
+  #extension GL_ANGLE_shader_pixel_local_storage : require
+  precision lowp float;
+  uniform vec4 color;
+  layout(binding=0, rgba8) uniform lowp pixelLocalANGLE pls;
+  void main() {
+    vec4 newColor = color + pixelLocalLoadANGLE(pls);
+    pixelLocalStoreANGLE(pls, newColor);
+  }`;
+
+  const program = wtu.setupProgram(localGL, [fullscreenQuadVertexShader, fs]);
+  if (!program) {
+    testFailed("Failed to compile program.");
+    return;
+  }
+
+  localGL.useProgram(program);
+  const colorUniLocation = localGL.getUniformLocation(program, "color");
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+
+  // Disable color mask to ensure PLS and canvas manage their own color masks properly.
+  localGL.colorMask(false, true, false, true);
+
+  // Set global variables for shouldBeTrue().
+  window.localGL = localGL;
+  window.localPLS = localPLS;
+
+  debug("\nCheck that pixel local storage works properly");
+  localGL.disable(localGL.DITHER);
+  localPLS.beginPixelLocalStorageWEBGL([localPLS.LOAD_OP_ZERO_WEBGL]);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+  shouldBeTrue("localGL.getParameter(localPLS.PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL) == 1");
+
+  localGL.uniform4f(colorUniLocation, 0, 1, 0, 0);
+  localGL.drawArrays(localGL.TRIANGLE_STRIP, 0, 4);
+
+  localPLS.pixelLocalStorageBarrierWEBGL();
+
+  localGL.uniform4f(colorUniLocation, 1, 0, 0, 0);
+  localGL.drawArrays(localGL.TRIANGLE_STRIP, 0, 4);
+
+  localPLS.endPixelLocalStorageWEBGL([localPLS.STORE_OP_STORE_WEBGL]);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+  shouldBeTrue("localGL.getParameter(localPLS.PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL) == 0");
+
+  const readFBO = localGL.createFramebuffer();
+  localGL.bindFramebuffer(localGL.READ_FRAMEBUFFER, readFBO);
+  localGL.framebufferTexture2D(localGL.READ_FRAMEBUFFER, localGL.COLOR_ATTACHMENT0,
+                               localGL.TEXTURE_2D, tex, 0);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+  wtu.checkCanvas(localGL, [255, 255, 0, 0]);
+
+  debug("\nCheck that alpha is properly handled in the main canvas.");
+  localGL.bindFramebuffer(localGL.DRAW_FRAMEBUFFER, null);
+  localGL.blitFramebuffer(0, 0, localCanvas.width, localCanvas.height, 0, 0, localCanvas.width,
+                          localCanvas.height, localGL.COLOR_BUFFER_BIT, localGL.NEAREST);
+  localGL.bindFramebuffer(localGL.FRAMEBUFFER, null);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+  wtu.checkCanvas(localGL, [255, 255, 0, alpha ? 0 : 255]);
+
+  localGL.bindFramebuffer(localGL.FRAMEBUFFER, plsFBO);
+  localPLS.beginPixelLocalStorageWEBGL([localPLS.LOAD_OP_LOAD_WEBGL]);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+  shouldBeTrue("localGL.getParameter(localPLS.PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL) == 1");
+
+  debug("\nGoing down from composite.");
+
+  // The canvas should get cleared after compositing, even if PLS is active and color mask is
+  // disabled.
+  await new Promise(resolve => wtu.waitForComposite(resolve));
+
+  // Reset global variables for shouldBeTrue() after await.
+  window.localGL = localGL;
+  window.localPLS = localPLS;
+
+  debug("\nBack from composite!");
+  debug("\nPLS should still be active on plsFBO even after being interrupted for compositing.");
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+  shouldBeTrue("localGL.getParameter(localPLS.PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL) == 1");
+
+  localGL.uniform4f(colorUniLocation, 0, 0, 1, 0);
+  localGL.drawArrays(localGL.TRIANGLE_STRIP, 0, 4);
+
+  localPLS.endPixelLocalStorageWEBGL([localPLS.STORE_OP_STORE_WEBGL]);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+  shouldBeTrue("localGL.getParameter(localPLS.PIXEL_LOCAL_STORAGE_ACTIVE_PLANES_WEBGL) == 0");
+
+  debug("\nThe canvas should have gotten cleared while PLS was active.");
+  localGL.bindFramebuffer(localGL.FRAMEBUFFER, null);
+  wtu.checkCanvas(localGL, [0, 0, 0, alpha ? 0 : 255]);
+
+  debug("\nThe additional PLS draw to plsFBO should have still worked after being interrupted " +
+        "for compositing.");
+  localGL.bindFramebuffer(localGL.READ_FRAMEBUFFER, readFBO);
+  wtu.checkCanvas(localGL, [255, 255, 255, 0]);
+  wtu.glErrorShouldBe(localGL, localGL.NONE);
+
+  // Draws 'tex' to the canvas.
+  const fs2 = `#version 300 es
+  uniform lowp sampler2D tex;
+  out lowp vec4 fragColor;
+  void main() {
+    ivec2 pixelCoord = ivec2(floor(gl_FragCoord.xy));
+    fragColor = texelFetch(tex, pixelCoord, 0);
+  }`;
+
+  const program2 = wtu.setupProgram(localGL, [fullscreenQuadVertexShader, fs2]);
+  if (!program2) {
+    testFailed("Failed to compile program2.");
+    return;
+  }
+
+  debug("\nBlue should still be disabled in the color mask. Alpha is not disabled but should be " +
+        "implicitly disabled since the canvas doesn't have alpha.");
+  localGL.useProgram(program2);
+  localGL.uniform1i(localGL.getUniformLocation(program2, "tex"), 0);
+  localGL.bindFramebuffer(localGL.FRAMEBUFFER, null);
+  localGL.drawArrays(localGL.TRIANGLE_STRIP, 0, 4);
+  wtu.checkCanvas(localGL, [0, 255, 0, alpha ? 0 : 255]);
+
+  debug("\nThe client's color mask should have been preserved.");
+  shouldBeTrue(`arraysEqual(localGL.getParameter(localGL.COLOR_WRITEMASK),
+                            [false, true, false, true])`);
+}
+
+runTest();
+var successfullyParsed = true;
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-stencil-texturing.html b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-stencil-texturing.html
new file mode 100644
index 0000000000..729a5bcf8a
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/extensions/webgl-stencil-texturing.html
@@ -0,0 +1,279 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL WEBGL_stencil_texturing Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of the WEBGL_stencil_texturing extension, if it is available.");
+
+debug("");
+
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext(null, null, 2);
+var ext;
+
+function runTestNoExtension() {
+    debug("");
+    debug("Check the texture parameter without the extension");
+
+    const tex = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, tex);
+
+    shouldBeNull("gl.getTexParameter(gl.TEXTURE_2D, 0x90EA /* DEPTH_STENCIL_TEXTURE_MODE_WEBGL */)");
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown without enabling the extension");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
+
+    gl.texParameteri(gl.TEXTURE_2D, 0x90EA /* DEPTH_STENCIL_TEXTURE_MODE_WEBGL */, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown for texParameteri without enabling the extension");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
+
+    gl.texParameterf(gl.TEXTURE_2D, 0x90EA /* DEPTH_STENCIL_TEXTURE_MODE_WEBGL */, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown for texParameterf without enabling the extension");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
+
+    const sampler = gl.createSampler();
+    gl.samplerParameteri(sampler, 0x90EA /* DEPTH_STENCIL_TEXTURE_MODE_WEBGL */, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown for samplerParameteri");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
+    gl.samplerParameterf(sampler, 0x90EA /* DEPTH_STENCIL_TEXTURE_MODE_WEBGL */, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown for samplerParameterf");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
+}
+
+function checkEnums() {
+    debug("");
+    debug("Check enums");
+    shouldBe("ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL", "0x90EA");
+    shouldBe("ext.STENCIL_INDEX_WEBGL",              "0x1901");
+}
+
+function checkQueries() {
+    const tex = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, tex);
+
+    debug("");
+    debug("Check default texture state");
+    shouldBe('gl.getTexParameter(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL)', 'gl.DEPTH_COMPONENT');
+    debug("");
+    debug("Check texture state updates using texParameteri");
+    gl.texParameteri(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, ext.STENCIL_INDEX_WEBGL);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    shouldBe('gl.getTexParameter(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL)', 'ext.STENCIL_INDEX_WEBGL');
+    gl.texParameteri(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    shouldBe('gl.getTexParameter(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL)', 'gl.DEPTH_COMPONENT');
+    gl.texParameteri(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, 0);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "invalid depth stencil mode value rejected by texParameteri");
+    shouldBe('gl.getTexParameter(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL)', 'gl.DEPTH_COMPONENT');
+    debug("");
+    debug("Check texture state updates using texParameterf");
+    gl.texParameterf(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, ext.STENCIL_INDEX_WEBGL);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    shouldBe('gl.getTexParameter(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL)', 'ext.STENCIL_INDEX_WEBGL');
+    gl.texParameterf(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    shouldBe('gl.getTexParameter(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL)', 'gl.DEPTH_COMPONENT');
+    gl.texParameterf(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, 0);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "invalid depth stencil mode value rejected by texParameterf");
+    shouldBe('gl.getTexParameter(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL)', 'gl.DEPTH_COMPONENT');
+
+    debug("");
+    debug("Check that depth stencil texture mode is not accepted as a sampler state");
+    const sampler = gl.createSampler();
+    gl.samplerParameteri(sampler, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown for samplerParameteri");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
+    gl.samplerParameterf(sampler, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, gl.DEPTH_COMPONENT);
+    wtu.glErrorShouldBe(gl, gl.INVALID_ENUM, "parameter unknown for samplerParameterf");
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no more errors");
+}
+
+function checkSampling() {
+    const formats = [
+        {name: "DEPTH_COMPONENT16", internalFormat: gl.DEPTH_COMPONENT16,
+         format: gl.DEPTH_COMPONENT, type: gl.UNSIGNED_SHORT},
+        {name: "DEPTH_COMPONENT24", internalFormat: gl.DEPTH_COMPONENT24,
+         format: gl.DEPTH_COMPONENT, type: gl.UNSIGNED_INT},
+        {name: "DEPTH_COMPONENT32F", internalFormat: gl.DEPTH_COMPONENT32F,
+         format: gl.DEPTH_COMPONENT, type: gl.FLOAT},
+        {name: "DEPTH24_STENCIL8", internalFormat: gl.DEPTH24_STENCIL8,
+         format: gl.DEPTH_STENCIL, type: gl.UNSIGNED_INT_24_8},
+        {name: "DEPTH32F_STENCIL8", internalFormat: gl.DEPTH32F_STENCIL8,
+         format: gl.DEPTH_STENCIL, type: gl.FLOAT_32_UNSIGNED_INT_24_8_REV}
+    ];
+
+    gl.enable(gl.DEPTH_TEST);
+    gl.enable(gl.STENCIL_TEST);
+    gl.stencilFunc(gl.ALWAYS, 170, 0xFF);
+    gl.stencilOp(gl.REPLACE, gl.REPLACE, gl.REPLACE);
+
+    wtu.setupUnitQuad(gl);
+
+    const drawProgram = wtu.setupProgram(gl, [wtu.simpleVertexShader,
+                                              wtu.simpleColorFragmentShader]);
+
+    const readDepthProgram = wtu.setupProgram(gl, [wtu.simpleTextureVertexShaderESSL300,
+                                                   wtu.simpleTextureFragmentShaderESSL300]);
+
+    const readStencilShader = `#version 300 es
+        precision highp float;
+        uniform highp usampler2D tex;
+        in vec2 texCoord;
+        out vec4 out_color;
+        void main() {
+            out_color = vec4(texture(tex, texCoord)) / 255.0;
+        }`;
+    const readStencilProgram = wtu.setupProgram(gl, [wtu.simpleTextureVertexShaderESSL300,
+                                                     readStencilShader]);
+
+    for (const format of formats) {
+        debug("");
+        debug(`Testing depth stencil texture modes with ${format.name}`);
+        const fbo = gl.createFramebuffer();
+        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+
+        const rbo = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, rbo);
+        gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA8, 1, 1);
+        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo);
+
+        const tex = gl.createTexture();
+        gl.bindTexture(gl.TEXTURE_2D, tex);
+        gl.texImage2D(gl.TEXTURE_2D, 0, format.internalFormat, 1, 1, 0, format.format, format.type, null);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "texture created");
+
+        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_2D, tex, 0);
+        if (format.format == gl.DEPTH_STENCIL) {
+            gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.TEXTURE_2D, tex, 0);
+        }
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+        gl.clear(gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
+        gl.useProgram(drawProgram);
+        wtu.drawUnitQuad(gl);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "no errors after drawing to the depth or depth stencil texture");
+
+        // Detach the depth or depth stencil texture to avoid feedback loop
+        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, null);
+        wtu.framebufferStatusShouldBe(gl, gl.FRAMEBUFFER, gl.FRAMEBUFFER_COMPLETE);
+
+        const magFilters = ['NEAREST', 'LINEAR'];
+
+        const minFilters = [
+            'NEAREST',
+            'LINEAR',
+            'NEAREST_MIPMAP_NEAREST',
+            'LINEAR_MIPMAP_NEAREST',
+            'NEAREST_MIPMAP_LINEAR',
+            'LINEAR_MIPMAP_LINEAR'
+        ];
+
+        const modes = [
+            [gl.DEPTH_COMPONENT, 'DEPTH_COMPONENT'],
+            [ext.STENCIL_INDEX_WEBGL, 'STENCIL_INDEX_WEBGL']
+        ];
+
+        const programs = [
+            [readDepthProgram, 'depth'],
+            [readStencilProgram, 'stencil']
+        ];
+
+        function validFilters(magFilter, minFilter) {
+            return magFilter == gl.NEAREST &&
+                   (minFilter == gl.NEAREST || minFilter == gl.NEAREST_MIPMAP_NEAREST);
+        }
+
+        for (const program of programs) {
+            gl.useProgram(program[0]);
+            for (const mode of modes) {
+                gl.texParameteri(gl.TEXTURE_2D, ext.DEPTH_STENCIL_TEXTURE_MODE_WEBGL, mode[0]);
+                for (const magFilter of magFilters) {
+                    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl[magFilter]);
+                    for (const minFilter of minFilters) {
+                        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl[minFilter]);
+                        debug(`Program: ${program[1]}, mode: ${mode[1]}, mag: ${magFilter}, min: ${minFilter}`);
+
+                        gl.clear(gl.COLOR_BUFFER_BIT);
+                        wtu.drawUnitQuad(gl);
+
+                        if (format.format == gl.DEPTH_COMPONENT || mode[0] == gl.DEPTH_COMPONENT) {
+                            if (program[1] == 'depth') {
+                                wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+                                if (validFilters(gl[magFilter], gl[minFilter])) {
+                                    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [128, 0, 0, 255], "sampling depth from complete texture", 1);
+                                } else {
+                                    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 0, 255], "sampling depth from incomplete texture", 1);
+                                }
+                            } else {
+                                wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "sampling depth using incompatible program");
+                            }
+                        } else {
+                            if (program[1] == 'stencil') {
+                                wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+                                if (validFilters(gl[magFilter], gl[minFilter])) {
+                                    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [170, 0, 0, 1], "sampling stencil from complete texture", 1);
+                                } else {
+                                    // Incomplete textures may produce [0, 0, 0, 1] or [0, 0, 0, 255].
+                                    const value = new Uint8Array(4);
+                                    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, value);
+                                    wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+                                    const msg = "sampling stencil from incomplete texture";
+                                    if (value[0] == 0 && value[1] == 0 && value[2] == 0 && (value[3] == 1 || value[3] == 255)) {
+                                        testPassed(msg);
+                                    } else {
+                                        testFailed(`${msg}: ${value}`);
+                                    }
+                                }
+                            } else {
+                                wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "sampling stencil using incompatible program");
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+function runTest() {
+    if (!gl) {
+        testFailed("context does not exist");
+        return;
+    }
+    testPassed("context exists");
+
+    runTestNoExtension();
+
+    ext = gl.getExtension("WEBGL_stencil_texturing");
+    wtu.runExtensionSupportedTest(gl, "WEBGL_stencil_texturing", ext !== null);
+
+    if (ext !== null) {
+        checkEnums();
+        checkQueries();
+        checkSampling();
+    } else {
+        testPassed("No WEBGL_stencil_texturing support -- this is legal");
+    }
+}
+
+runTest();
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/00_test_list.txt
index 5a47d470f9..9e8bc87a62 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/00_test_list.txt
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/00_test_list.txt
@@ -41,6 +41,7 @@ shader-with-invalid-characters.html
 shader-with-mis-matching-uniform-block.html
 short-circuiting-in-loop-condition.html
 --min-version 2.0.1 switch-case.html
+--min-version 2.0.1 texture-bias.html
 --min-version 2.0.1 texture-offset-non-constant-offset.html
 texture-offset-out-of-range.html
 --min-version 2.0.1 texture-offset-uniform-texture-coordinate.html
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/texture-bias.html b/dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/texture-bias.html
new file mode 100644
index 0000000000..0c30eb7129
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/glsl3/texture-bias.html
@@ -0,0 +1,146 @@
+<!--
+Copyright (c) 2022 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>GLSL texture bias test</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+<script src="../../js/glsl-conformance-test.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("Texture bias should both function and respect limits.");
+
+function runTest(gl) {
+  // no if idea any drivers have a giant limit like 2^32 so just in case.
+  const kMaxMaxTextureSize = 256 * 1024 * 1024;
+  const maxTextureSize = Math.min(kMaxMaxTextureSize, gl.getParameter(gl.MAX_TEXTURE_SIZE));
+  const maxLODs = (Math.log2(maxTextureSize) | 0) + 1;
+  const maxTextureLODBias = gl.getParameter(gl.MAX_TEXTURE_LOD_BIAS);
+
+  debug(`maxTextureSize: ${maxTextureSize}`);
+  debug(`maxLODs: ${maxLODs}`);
+  debug(`maxTextureLODBias: ${maxTextureLODBias}`);
+
+  const vs = `#version 300 es
+  uniform float uvMult;
+  out vec2 v_uv;
+  void main() {
+    vec2 xy = vec2(
+      gl_VertexID % 2,
+      (gl_VertexID / 2 + gl_VertexID / 3) % 2);
+
+    gl_Position = vec4(xy * 2. - 1.0, 0, 1);
+    v_uv = xy * uvMult;
+  }
+  `;
+  const fs = `#version 300 es
+  precision highp float;
+  uniform sampler2D tex;
+  uniform float biasMult;
+  in vec2 v_uv;
+  out vec4 fragColor;
+  void main() {
+    vec4 texColor = texture(tex, v_uv, (gl_FragCoord.x - 0.5) * biasMult);  // the color we care about
+    vec4 texelColor = texelFetch(tex, ivec2(0), int(gl_FragCoord));         // just a sanity check
+    vec4 coordColor = vec4((100.0 + gl_FragCoord.x - 0.5) / 255.0);         // another sanity check
+    fragColor = mix(texColor, coordColor, step(1.0, gl_FragCoord.y));       // line < 1 = texColor, line >= 1 = coordColor
+    fragColor = mix(fragColor, texelColor, step(2.0, gl_FragCoord.y));      // line < 2 = fragColor, line >= 2 = texelColor
+  }
+  `;
+  const program = wtu.setupProgram(gl, [vs, fs]);
+  const uvMultLoc = gl.getUniformLocation(program, 'uvMult');
+  const biasLoc = gl.getUniformLocation(program, 'biasMult');
+
+  gl.canvas.width = maxLODs;
+  gl.canvas.height = 3;
+  gl.viewport(0, 0, maxLODs, 3);
+
+  // create a texture where each mip is a different color (1, 2, 3, ...)
+  const tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST_MIPMAP_NEAREST);
+  gl.texStorage2D(gl.TEXTURE_2D, maxLODs, gl.RGBA8, maxTextureSize, 1);
+  {
+    let level = 0;
+    for (let width = maxTextureSize; width > 0; width = width / 2 | 0) {
+      const pixels = new Uint8Array(width * 1 * 4);
+      pixels.fill(level + 1);
+      debug(`fill mip level: ${level}, width: ${width}`);
+      gl.texSubImage2D(gl.TEXTURE_2D, level, 0, 0, width, 1, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
+      wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+      ++level;
+    }
+  }
+
+  // Draw each mip. Result should be [mip0, mip1, mip2, ...]
+  debug("");
+  debug("check positive bias");
+  // set the UVs so we'd get mip level 0 for every pixel
+  gl.uniform1f(uvMultLoc, maxLODs / maxTextureSize);
+  gl.uniform1f(biasLoc, 1);
+  gl.drawArrays(gl.TRIANGLES, 0, 6);
+
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+  const clampPlusMinus = (v, limit) => Math.min(limit, Math.max(-limit, v));
+
+  const checkResults = (gl, biasMult) => {
+    const base = biasMult > 0 ? 1 : maxLODs;
+    for (let i = 0; i < maxLODs; ++i) {
+      {
+        const expected = new Array(4).fill(clampPlusMinus(i * biasMult, maxTextureLODBias) + base);
+        wtu.checkCanvasRect(gl, i, 0, 1, 1, expected, `should be: ${expected}`);
+      }
+      {
+        const expected = new Array(4).fill(100 + i);
+        wtu.checkCanvasRect(gl, i, 1, 1, 1, expected, `should be: ${expected}`);
+      }
+      {
+        const expected = new Array(4).fill(i + 1);
+        wtu.checkCanvasRect(gl, i, 2, 1, 1, expected, `should be: ${expected}`);
+      }
+    }
+  }
+
+  checkResults(gl, 1);
+
+  // Draw each mip. Result should be [mipMax, mipMax - 1, mipMax - 2, ...]
+  debug("");
+  debug("check negative bias");
+  // set the UVs so we'd get highest mip level (the 1x1 level mip) for every pixel
+  gl.uniform1f(uvMultLoc, maxLODs);
+  gl.uniform1f(biasLoc, -1);
+  gl.drawArrays(gl.TRIANGLES, 0, 6);
+
+  checkResults(gl, -1);
+
+  finishTest();
+}
+
+const wtu = WebGLTestUtils;
+
+const gl = wtu.create3DContext(undefined, undefined, 2);
+
+var successfullyParsed = true;
+
+if (!gl) {
+  testFailed("Unable to initialize WebGL 2.0 context.");
+} else {
+  runTest(gl);
+}
+
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/query/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/query/00_test_list.txt
index c40921bf88..a2e21b5ad7 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/query/00_test_list.txt
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/query/00_test_list.txt
@@ -1,2 +1,3 @@
 occlusion-query.html
+--min-version 2.0.1 occlusion-query-scissor.html 
 query.html
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/query/occlusion-query-scissor.html b/dom/canvas/test/webgl-conf/checkout/conformance2/query/occlusion-query-scissor.html
new file mode 100644
index 0000000000..dec88e56d3
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/query/occlusion-query-scissor.html
@@ -0,0 +1,117 @@
+<!--
+Copyright (c) 2022 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>WebGL Occlusion Query w/Scissor Conformance Tests</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<canvas id="canvas" style="width: 50px; height: 50px;"> </canvas>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test verifies the functionality of occlusion query objects with the scissor test.");
+debug('Regression test for <a href="http://anglebug.com/7157">http://anglebug.com/7157</a>');
+
+debug("");
+
+const wtu = WebGLTestUtils;
+
+const wait = () => new Promise(resolve => setTimeout(resolve));
+
+async function runOcclusionQueryTest(gl) {
+    const kSize = 4;
+    const colors = [
+      [0, 0, 0, 255],
+      [255, 0, 0, 255],
+      [0, 255, 0, 255],
+      [255, 255, 0, 255],
+    ];
+    const framebuffers = colors.map((color, index) => {
+      const tex = gl.createTexture();
+      gl.bindTexture(gl.TEXTURE_2D, tex);
+      gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, kSize, kSize, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+
+      const fb = gl.createFramebuffer();
+      gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+      gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
+
+      gl.clearColor(index & 1, (index >> 1) & 1, (index >> 2) & 1, 1);
+      gl.clear(gl.COLOR_BUFFER_BIT);
+
+      wtu.checkCanvasRect(gl, 0, 0, kSize, kSize, color);
+
+      return fb;
+    });
+
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "setup should succeed");
+
+    gl.viewport(0, 0, kSize, kSize);
+
+    const program = wtu.setupSimpleColorProgram(gl, 0);
+    gl.uniform4f(gl.getUniformLocation(program, "u_color"), 0, 1, 0, 1);
+    wtu.setupUnitQuad(gl, 0);
+
+    const query = gl.createQuery();;
+
+    for (let i = 0; i < 256; ++i)
+    {
+        gl.beginQuery(gl.ANY_SAMPLES_PASSED, query);
+        let drawn = false;
+
+        framebuffers.forEach((fb, index) => {
+            gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+            const scissor = (i >> 4 >> index) & 1;
+            if (i & (1 << index))
+            {
+                if (scissor)
+                {
+                    gl.enable(gl.SCISSOR_TEST);
+                    gl.scissor(0, 0, 0, 0);
+                }
+                wtu.drawUnitQuad(gl);
+                drawn ||= !scissor;
+                if (scissor)
+                {
+                    gl.disable(gl.SCISSOR_TEST);
+                    gl.scissor(0, 0, kSize, kSize);
+                }
+            }
+        });
+
+        gl.endQuery(gl.ANY_SAMPLES_PASSED);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should draw");
+
+        do {
+          await wait();
+        } while (!gl.getQueryParameter(query, gl.QUERY_RESULT_AVAILABLE));
+
+        const result = gl.getQueryParameter(query, gl.QUERY_RESULT);
+
+        const expected = drawn ? 1 : 0;
+        assertMsg(result === expected, `pass ${i}, result: ${result} === expected: ${expected}`);
+    }
+    finishTest();
+}
+
+const canvas = document.getElementById("canvas");
+const gl = wtu.create3DContext(canvas, null, 2);
+
+if (!gl) {
+    testFailed("WebGL context does not exist");
+} else {
+    testPassed("WebGL context exists");
+    runOcclusionQueryTest(gl);
+}
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-object-attachment.html b/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-object-attachment.html
index 754ff2cc73..bc4d623446 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-object-attachment.html
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-object-attachment.html
@@ -111,9 +111,10 @@ function testFramebufferWebGL1RequiredCombinations() {
     gl.deleteFramebuffer(fbo);
 }
 
-function testDepthStencilAttachmentBehaviors() {
+function testDepthStencilAttachmentBehaviors(testOrphanedRenderbuffers) {
+    let suffix = testOrphanedRenderbuffers ? " with deleted renderbuffer" : "";
     debug("");
-    debug("Checking ES3 DEPTH_STENCIL_ATTACHMENT behaviors are implemented for WebGL 2");
+    debug("Checking ES3 DEPTH_STENCIL_ATTACHMENT behaviors are implemented for WebGL 2" + suffix);
     // DEPTH_STENCIL_ATTACHMENT is treated as an independent attachment point in WebGL 1;
     // however, in WebGL 2, it is treated as an alias for DEPTH_ATTACHMENT + STENCIL_ATTACHMENT.
     var size = 16;
@@ -127,24 +128,45 @@ function testDepthStencilAttachmentBehaviors() {
     gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA8, size, size);
     checkFramebuffer([gl.FRAMEBUFFER_COMPLETE]);
 
-    var depthBuffer = gl.createRenderbuffer();
-    gl.bindRenderbuffer(gl.RENDERBUFFER, depthBuffer);
-    gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, size, size);
+    function createDepthBuffer() {
+        let buffer = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, buffer);
+        gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, size, size);
+        gl.bindRenderbuffer(gl.RENDERBUFFER, null);
+        return buffer;
+    }
+
+    function createStencilBuffer() {
+        let buffer = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, buffer);
+        gl.renderbufferStorage(gl.RENDERBUFFER, gl.STENCIL_INDEX8, size, size);
+        gl.bindRenderbuffer(gl.RENDERBUFFER, null);
+        return buffer;
+    }
 
-    var stencilBuffer = gl.createRenderbuffer();
-    gl.bindRenderbuffer(gl.RENDERBUFFER, stencilBuffer);
-    gl.renderbufferStorage(gl.RENDERBUFFER, gl.STENCIL_INDEX8, size, size);
+    function createDepthStencilBuffer() {
+        let buffer = gl.createRenderbuffer();
+        gl.bindRenderbuffer(gl.RENDERBUFFER, buffer);
+        gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_STENCIL, size, size);
+        gl.bindRenderbuffer(gl.RENDERBUFFER, null);
+        return buffer;
+    }
 
-    var depthStencilBuffer = gl.createRenderbuffer();
-    gl.bindRenderbuffer(gl.RENDERBUFFER, depthStencilBuffer);
-    gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_STENCIL, size, size);
+    function orphan(renderbuffer) {
+        gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+        gl.deleteRenderbuffer(renderbuffer);
+        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+    }
 
     wtu.glErrorShouldBe(gl, gl.NO_ERROR);
 
     debug("");
-    debug("color + depth");
+    debug("color + depth" + suffix);
+    var depthBuffer = createDepthBuffer();
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, depthBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
@@ -153,9 +175,12 @@ function testDepthStencilAttachmentBehaviors() {
     checkBufferBits(gl.DEPTH_ATTACHMENT);
 
     debug("");
-    debug("color + depth + stencil: depth != stencil");
+    debug("color + depth + stencil: depth != stencil" + suffix);
+    var stencilBuffer = createStencilBuffer();
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.RENDERBUFFER, stencilBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(stencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", stencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
@@ -170,9 +195,12 @@ function testDepthStencilAttachmentBehaviors() {
     wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
 
     debug("");
-    debug("color + depth: DEPTH_STENCIL for DEPTH_ATTACHMENT");
+    debug("color + depth: DEPTH_STENCIL for DEPTH_ATTACHMENT" + suffix);
+    var depthStencilBuffer = createDepthStencilBuffer();
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
@@ -181,9 +209,16 @@ function testDepthStencilAttachmentBehaviors() {
     checkBufferBits(gl.DEPTH_ATTACHMENT);
 
     debug("");
-    debug("color + depth + stencil: DEPTH_STENCIL for DEPTH_ATTACHMENT and STENCIL_ATTACHMENT");
+    debug("color + depth + stencil: DEPTH_STENCIL for DEPTH_ATTACHMENT and STENCIL_ATTACHMENT" + suffix);
+    if (testOrphanedRenderbuffers) {
+        depthStencilBuffer = createDepthStencilBuffer();
+        gl.framebufferRenderbuffer(
+            gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
+    }
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
@@ -192,7 +227,7 @@ function testDepthStencilAttachmentBehaviors() {
     checkBufferBits(gl.DEPTH_STENCIL_ATTACHMENT);
 
     debug("");
-    debug("color + depth_stencil");
+    debug("color + depth_stencil" + suffix);
     var texture = gl.createTexture();
     gl.bindTexture(gl.TEXTURE_2D, texture);
     gl.texImage2D(gl.TEXTURE_2D, 0, gl.DEPTH24_STENCIL8, size, size, 0, gl.DEPTH_STENCIL, gl.UNSIGNED_INT_24_8, null);
@@ -209,8 +244,12 @@ function testDepthStencilAttachmentBehaviors() {
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
     wtu.glErrorShouldBe(gl, gl.NO_ERROR);
 
+    if (testOrphanedRenderbuffers)
+        depthStencilBuffer = createDepthStencilBuffer();
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
@@ -219,16 +258,24 @@ function testDepthStencilAttachmentBehaviors() {
     checkBufferBits(gl.DEPTH_STENCIL_ATTACHMENT);
 
     debug("");
-    debug("DEPTH_STENCIL_ATTACHMENT overwrites DEPTH_ATTACHMENT/STENCIL_ATTACHMENT")
+    debug("DEPTH_STENCIL_ATTACHMENT overwrites DEPTH_ATTACHMENT/STENCIL_ATTACHMENT" + suffix);
+    if (testOrphanedRenderbuffers)
+        depthBuffer = createDepthBuffer();
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, depthBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
     wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
 
+    if (testOrphanedRenderbuffers)
+        depthStencilBuffer = createDepthStencilBuffer();
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
@@ -244,9 +291,13 @@ function testDepthStencilAttachmentBehaviors() {
     checkBufferBits();
 
     debug("");
-    debug("STENCIL_ATTACHMENT overwrites stencil set by DEPTH_STENCIL_ATTACHMENT")
+    debug("STENCIL_ATTACHMENT overwrites stencil set by DEPTH_STENCIL_ATTACHMENT" + suffix);
+    if (testOrphanedRenderbuffers)
+        depthStencilBuffer = createDepthStencilBuffer();
     gl.framebufferRenderbuffer(
         gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
     shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
@@ -260,6 +311,28 @@ function testDepthStencilAttachmentBehaviors() {
     wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
     checkFramebuffer([gl.FRAMEBUFFER_COMPLETE]);
     checkBufferBits(gl.DEPTH_ATTACHMENT);
+
+    debug("");
+    debug("DEPTH_ATTACHMENT overwrites depth set by DEPTH_STENCIL_ATTACHMENT" + suffix);
+    if (testOrphanedRenderbuffers)
+        depthStencilBuffer = createDepthStencilBuffer();
+    gl.framebufferRenderbuffer(
+        gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthStencilBuffer);
+    if (testOrphanedRenderbuffers)
+        orphan(depthStencilBuffer);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+    gl.framebufferRenderbuffer(
+        gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, null);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", depthStencilBuffer);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", null);
+    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
+    checkFramebuffer([gl.FRAMEBUFFER_COMPLETE]);
+    checkBufferBits(gl.STENCIL_ATTACHMENT);
 }
 
 function testFramebufferIncompleteAttachment() {
@@ -469,7 +542,8 @@ description("Test framebuffer object attachment behaviors");
 shouldBeNonNull("gl = wtu.create3DContext(undefined, undefined, 2)");
 
 testFramebufferWebGL1RequiredCombinations();
-testDepthStencilAttachmentBehaviors();
+testDepthStencilAttachmentBehaviors(false);
+testDepthStencilAttachmentBehaviors(true);
 testFramebufferIncompleteAttachment();
 testFramebufferIncompleteMissingAttachment();
 testFramebufferWithImagesOfDifferentSizes();
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-texture-layer.html b/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-texture-layer.html
index 0e435d6a2e..13e5d790e8 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-texture-layer.html
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/renderbuffers/framebuffer-texture-layer.html
@@ -121,6 +121,37 @@ function testFramebufferTextureLayer() {
         "attaching a depth_stencil texture to a framebuffer should succeed.");
     checkFramebuffer([gl.FRAMEBUFFER_COMPLETE]);
 
+    var texDepthStencil = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D_ARRAY, texDepthStencil);
+
+    var texDepthStencilMany = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D_ARRAY, texDepthStencilMany);
+    var fbDepthStencilMany = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fbDepthStencilMany);
+    gl.texImage3D(gl.TEXTURE_2D_ARRAY,
+                  0,                                          // level
+                  gl.DEPTH24_STENCIL8,                        // internalFormat
+                  1,                                          // width
+                  1,                                          // height
+                  2,                                          // depth
+                  0,                                          // border
+                  gl.DEPTH_STENCIL,                           // format
+                  gl.UNSIGNED_INT_24_8,                       // type
+                  new Uint32Array([0, 1]));                      // data
+
+    gl.framebufferTextureLayer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, texDepthStencilMany, 0, 0);
+    gl.framebufferTextureLayer(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, texDepthStencilMany, 0, 0);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR,
+        "attaching a depth_stencil 2d array texture level 0 to a framebuffer should succeed.");
+    checkFramebuffer([gl.FRAMEBUFFER_COMPLETE]);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", texDepthStencilMany);
+    gl.framebufferTextureLayer(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, texDepthStencilMany, 0, 1);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR,
+        "attaching a 2d array texture level 0 to depth and layer 1 to stencil attachment of a framebuffer should succeed.");
+    // "Depth and stencil attachments, if present, are the same image." If not, then "FRAMEBUFFER_UNSUPPORTED".
+    checkFramebuffer([gl.FRAMEBUFFER_UNSUPPORTED]);
+    shouldEvaluateTo("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", texDepthStencilMany);
+
     // Clean up
     gl.deleteTexture(tex3d);
     gl.deleteTexture(texDepthStencil);
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/rendering/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/rendering/00_test_list.txt
index 92ce232ee2..c4a1bbe9e8 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/rendering/00_test_list.txt
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/rendering/00_test_list.txt
@@ -11,7 +11,6 @@ blitframebuffer-size-overflow.html
 --min-version 2.0.1 blitframebuffer-stencil-only.html
 blitframebuffer-test.html
 --min-version 2.0.1 blitframebuffer-unaffected-by-colormask.html
---min-version 2.0.1 builtin-vert-attribs.html
 canvas-resizing-with-pbo-bound.html
 --min-version 2.0.1 clearbuffer-sub-source.html
 --min-version 2.0.1 clearbufferfv-with-alpha-false.html
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/rendering/builtin-vert-attribs.html b/dom/canvas/test/webgl-conf/checkout/conformance2/rendering/builtin-vert-attribs.html
deleted file mode 100644
index cc64c9034b..0000000000
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/rendering/builtin-vert-attribs.html
+++ /dev/null
@@ -1,408 +0,0 @@
-<!--
-Copyright (c) 2022 The Khronos Group Inc.
-Use of this source code is governed by an MIT-style license that can be
-found in the LICENSE.txt file.
--->
-
-<!DOCTYPE html>
-<html>
-<head>
-<meta charset=utf-8>
-<link rel=stylesheet href="../../resources/js-test-style.css"/>
-<script src="../../js/js-test-pre.js"></script>
-<script src="../../js/webgl-test-utils.js"></script>
-</head>
-<body>
-<canvas id=e_canvas width=1 height=1 style="width: 100px; height: 100px;"></canvas>
-<div id=description></div>
-<div id=console></div>
-<script>
-"use strict";
-description('gl_VertexID and gl_InstanceID should behave as per spec.');
-
-//
-
-/*
-So what are gl_VertexID and gl_InstanceID supposed to do?
-In ES 3.0 and GL 4.1 (Core), this is all we get:
-
-# ES 3.0
-
-> (p78) gl_VertexID holds the integer index i implicitly passed by DrawArrays or
-> one of the other drawing commands defined in section 2.9.3. The value of
-> gl_VertexID is defined if and only if all enabled vertex arrays have non-zero buffer
-> object bindings.
-> gl_InstanceID holds the integer instance number of the current primitive in
-> an instanced draw call (see section 2.9.3).
-
-
-# GL 4.1 (Core)
-
-> (p102) gl_VertexID holds the integer index i implicitly passed by DrawArrays or
-> one of the other drawing commands defined in section 2.8.3.
-> gl_InstanceID holds the integer index of the current primitive in an
-> instanced draw call (see section 2.8.3).
-
-
-# ES 3.1
-
-ES 3.1 retains the wording from ES 3.0, but adds the following clarifications:
-
-gl_VertexID:
-> (p252) The index of any element transferred to the GL by DrawArraysOneInstance
-> is referred to as its vertex ID, and may be read by a vertex shader as gl_VertexID.
-> The vertex ID of the ith element transferred is first + i.
-
-> (p254) The index of any element transferred to the GL by
-> DrawElementsOneInstance is referred to as its vertex ID, and may be read by a vertex shader as
-> gl_VertexID. If no element array buffer is bound, the vertex ID of the ith element
-> transferred is indices[i] + basevertex. Otherwise, the vertex ID of the ith
-> element transferred is the sum of basevertex and the value stored in the currently
-> bound element array buffer at offset indices + i.
-
-gl_InstanceID
-> (p255) If an enabled vertex attribute array is instanced (it has a non-zero divisor as
-> specified by VertexAttribDivisor), the element index that is transferred to the GL,
-> for all vertices, is given by
-> `floor(instance / divisor) + baseinstance`
-
-
-# Errata
-
-Drivers generally do implement the ES 3.1 behavior.
-A notable exception is Mac's legacy GL (4.1) driver which has two bugs here.
-(Both ANGLE-on-Metal and the system M1+ GL driver seem correct though)
-
-## gl_InstanceID random for DrawArrays calls
-Use ERRATA.IGNORE_GL_INSTANCE_ID to cause these tests to pass.
-
-## Adds `first` to user-attrib instanced fetch ids in DrawArrays calls.
-Use ERRATA.FIRST_ADDS_TO_INSTANCE to cause these tests to pass.
-*/
-
-const wtu = WebGLTestUtils;
-const gl = wtu.create3DContext('e_canvas');
-
-const ERRATA = {};
-//ERRATA.IGNORE_GL_INSTANCE_ID = true; // Chrome on ANGLE-on-Mac-GL needs this.
-//ERRATA.FIRST_ADDS_TO_INSTANCE = true; // Firefox with MOZ_WEBGL_WORKAROUND_FIRST_AFFECTS_INSTANCE_ID=0 would need this.
-
-debug(`ERRATA: ${JSON.stringify(ERRATA)}`);
-
-function make_vs_point(vid, iid) {
-    return `\
-    #version 300 es
-
-    ${vid.name == 'gl_VertexID' ? '// ' : ''}layout(location=${vid.loc}) in highp int ${vid.name};
-    ${iid.name == 'gl_InstanceID' ? '// ' :''}layout(location=${iid.loc}) in highp int ${iid.name};
-    out vec4 v_color;
-
-    void main() {
-        gl_PointSize = 1.0;
-        gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
-        v_color = vec4(1.0, float(${vid.name}) / 255.0, float(${iid.name}) / 255.0, 1.0);
-#if ${(iid.name == 'gl_InstanceID' && ERRATA.IGNORE_GL_INSTANCE_ID)|0}
-        v_color.b = 0.0;
-#endif
-    }`;
-}
-
-function make_vs_tri(vid, iid) {
-    return `\
-    #version 300 es
-
-    ${vid.name == 'gl_VertexID' ? '// ' : ''}layout(location=${vid.loc}) in highp int ${vid.name};
-    ${iid.name == 'gl_InstanceID' ? '// ' :''}layout(location=${iid.loc}) in highp int ${iid.name};
-    out vec4 v_color;
-
-    void main() {
-        int prim_vert_id = ${vid.name} % 3;
-        int flat_vert_id = ${vid.name} - prim_vert_id + 2;
-        gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
-        gl_Position.x = (prim_vert_id == 1) ? 2.0 : -1.0;
-        gl_Position.y = (prim_vert_id == 2) ? 2.0 : -1.0;
-        v_color = vec4(1.0, float(flat_vert_id) / 255.0, float(${iid.name}) / 255.0, 1.0);
-#if ${(iid.name == 'gl_InstanceID' && ERRATA.IGNORE_GL_INSTANCE_ID)|0}
-        v_color.b = 0.0;
-#endif
-    }`;
-}
-
-const FS = `\
-    #version 300 es
-    precision mediump float;
-
-    in vec4 v_color;
-    out vec4 o_color;
-
-    void main() {
-        o_color = v_color;
-    }
-`;
-
-
-function crossCombine(...args) {
-  function crossCombine2(listA, listB) {
-    const listC = [];
-    for (const a of listA) {
-      for (const b of listB) {
-        const c = Object.assign({}, a, b);
-        listC.push(c);
-      }
-    }
-    return listC;
-  }
-
-  let res = [{}];
-  while (args.length) {
-    const next = args.shift();
-    next[0].defined;
-    res = crossCombine2(res, next);
-  }
-  return res;
-}
-
-/// makeCombiner('foo', [5, 3]) -> [{foo: 5}, {foo: 3}]
-function makeCombiner(key, vals) {
-  const ret = [];
-  for (const val of vals) {
-      const cur = {};
-      cur[key] = val;
-      ret.push(cur);
-  }
-  return ret;
-}
-
-debug('Draw a point with a shader that takes no attributes and verify it fills the whole canvas.');
-
-
-let TESTS = [
-    makeCombiner('vid', [
-        {name: 'a_VertexID', loc:0},
-        {name: 'a_VertexID', loc:2}, // Test 2, so that we're not only testing 0.
-        {name: 'gl_VertexID', loc:-1},
-        {name: 'gl_VertexID', loc:0}, // Enable a vertex array, despite not using it.
-        {name: 'gl_VertexID', loc:2}, // Enable a vertex array, despite not using it.
-    ]),
-    makeCombiner('iid', [
-        {name: 'a_InstanceID', loc:1},
-        {name: 'gl_InstanceID', loc:-1},
-        {name: 'gl_InstanceID', loc:1}, // Enable a vertex array, despite not using it.
-    ]),
-    makeCombiner('separate_vbufs', [true, false]),
-];
-//console.log('a', {TESTS});
-TESTS = crossCombine(...TESTS);
-//console.log('b', {TESTS});
-
-
-let vdata = new Int32Array(1000);
-vdata = vdata.map((v,i) => i);
-const vbuf = gl.createBuffer();
-gl.bindBuffer(gl.ARRAY_BUFFER, vbuf);
-gl.bufferData(gl.ARRAY_BUFFER, vdata, gl.STATIC_DRAW);
-
-
-const vbuf2 = gl.createBuffer();
-gl.bindBuffer(gl.ARRAY_BUFFER, vbuf2);
-gl.bufferData(gl.ARRAY_BUFFER, vdata, gl.STATIC_DRAW);
-
-
-let index_data = new Uint32Array(1000);
-index_data = index_data.map((x,i) => 10+i);
-const index_buffer = gl.createBuffer();
-gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, index_buffer);
-gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, index_data, gl.STATIC_DRAW);
-
-
-gl.disable(gl.DEPTH_TEST);
-
-(async () => {
-    for (const desc of TESTS) {
-        await wtu.dispatchPromise(); // Yield, for responsiveness.
-        debug('');
-        debug('---------------------');
-        debug(`desc: ${JSON.stringify(desc)}`);
-
-        let fn = (vs) => {
-            //console.log({vs});
-            const prog = wtu.setupProgram(gl, [vs, FS]);
-
-            {
-                const WEBGL_debug_shaders = gl.getExtension('WEBGL_debug_shaders');
-                let i = -1;
-                for (const s of gl.getAttachedShaders(prog)) {
-                    i += 1;
-                    debug('');
-                    debug(`shader[${i}] getShaderSource() -> `);
-                    debug(gl.getShaderSource(s));
-                    if (WEBGL_debug_shaders) {
-                        debug(`shader[${i}] getTranslatedShaderSource() -> `);
-                        debug(WEBGL_debug_shaders.getTranslatedShaderSource(s));
-                    }
-                }
-            }
-            return prog;
-        };
-        const point_prog = fn(make_vs_point(desc.vid, desc.iid));
-        const tri_prog = fn(make_vs_tri(desc.vid, desc.iid));
-
-        // -
-
-        gl.bindBuffer(gl.ARRAY_BUFFER, null);
-        for (let i = 0; i <= 2; i++) {
-            gl.disableVertexAttribArray(i);
-            gl.vertexAttribPointer(i, 4, gl.FLOAT, false, 0, 0);
-            gl.vertexAttribDivisor(i, 0);
-        }
-
-        gl.bindBuffer(gl.ARRAY_BUFFER, vbuf);
-        let loc = desc.vid.loc;
-        if (loc != -1) {
-            gl.enableVertexAttribArray(loc);
-            gl.vertexAttribIPointer(loc, 1, gl.INT, 0, 0);
-        };
-
-        if (desc.separate_vbufs) {
-            gl.bindBuffer(gl.ARRAY_BUFFER, vbuf2);
-        }
-        loc = desc.iid.loc;
-        if (loc != -1) {
-            gl.enableVertexAttribArray(loc);
-            gl.vertexAttribIPointer(loc, 1, gl.INT, 0, 0);
-            gl.vertexAttribDivisor(loc, 1);
-        };
-
-        {
-            const err = gl.getError();
-            if (err) throw err; // Broken init.
-        }
-
-        // -
-
-        fn = (eval_str, expected_arr) => {
-            if (ERRATA.IGNORE_GL_INSTANCE_ID) {
-                if (desc.iid.name == 'gl_InstanceID') {
-                    expected_arr = expected_arr.map(x => x);
-                    expected_arr[2] = 0;
-                }
-            }
-
-            debug('');
-            //debug(`${eval_str} -> [${expected_arr.join(', ')}]`);
-            eval(eval_str);
-
-            const err = gl.getError();
-            if (err) throw err; // Broken subtest.
-
-            wtu.checkCanvas(gl, expected_arr, eval_str);
-        }
-
-        gl.useProgram(point_prog);
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawArrays(gl.POINTS,   0, 0)`, [0, 0, 0, 0]);
-        fn(`gl.drawArrays(gl.POINTS,   0, 1)`, [255, 0, 0, 255]);
-        fn(`gl.drawArrays(gl.POINTS,   0, 2)`, [255, 1, 0, 255]);
-        if (ERRATA.FIRST_ADDS_TO_INSTANCE) {
-            fn(`gl.drawArrays(gl.POINTS, 100, 2)`, [255, 100+2-1, 100, 255]);
-        } else {
-            fn(`gl.drawArrays(gl.POINTS, 100, 2)`, [255, 100+2-1, 0, 255]);
-        }
-        fn(`gl.drawArrays(gl.POINTS, 0, 255)`, [255, 254, 0, 255]);
-        fn(`gl.drawArrays(gl.POINTS, 0, 256)`, [255, 255, 0, 255]);
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawArraysInstanced(gl.POINTS,   0, 0, 1)`, [0, 0, 0, 0]);
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawArraysInstanced(gl.POINTS,   0, 1, 0)`, [0, 0, 0, 0]);
-
-        fn(`gl.drawArraysInstanced(gl.POINTS,   0, 1, 1)`, [255, 0, 0, 255]);
-        fn(`gl.drawArraysInstanced(gl.POINTS,   0, 2, 1)`, [255, 1, 0, 255]);
-        fn(`gl.drawArraysInstanced(gl.POINTS,   0, 1, 2)`, [255, 0, 1, 255]);
-        fn(`gl.drawArraysInstanced(gl.POINTS,   0, 2, 2)`, [255, 1, 1, 255]);
-        if (ERRATA.FIRST_ADDS_TO_INSTANCE) {
-            fn(`gl.drawArraysInstanced(gl.POINTS, 100, 2, 2)`, [255, 100+2-1, 101, 255]);
-        } else {
-            fn(`gl.drawArraysInstanced(gl.POINTS, 100, 2, 2)`, [255, 100+2-1, 1, 255]);
-        }
-        fn(`gl.drawArraysInstanced(gl.POINTS,   0, 255, 255)`, [255, 254, 254, 255]);
-
-        // -
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawElements(gl.POINTS,   0, gl.UNSIGNED_INT, 4*0)`, [0, 0, 0, 0]);
-        fn(`gl.drawElements(gl.POINTS,   1, gl.UNSIGNED_INT, 4*0)`, [255, 10+0, 0, 255]);
-        fn(`gl.drawElements(gl.POINTS,   2, gl.UNSIGNED_INT, 4*0)`, [255, 10+1, 0, 255]);
-        fn(`gl.drawElements(gl.POINTS,   2, gl.UNSIGNED_INT, 4*100)`, [255, 100+10+1, 0, 255]);
-        fn(`gl.drawElements(gl.POINTS, 245, gl.UNSIGNED_INT, 4*0)`, [255, 10+244, 0, 255]);
-        fn(`gl.drawElements(gl.POINTS, 246, gl.UNSIGNED_INT, 4*0)`, [255, 10+245, 0, 255]);
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawElementsInstanced(gl.POINTS,   0, gl.UNSIGNED_INT, 4*0, 1)`, [0, 0, 0, 0]);
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawElementsInstanced(gl.POINTS,   1, gl.UNSIGNED_INT, 4*0, 0)`, [0, 0, 0, 0]);
-
-        fn(`gl.drawElementsInstanced(gl.POINTS,   1, gl.UNSIGNED_INT, 4*0, 1)`, [255, 10+0, 0, 255]);
-        fn(`gl.drawElementsInstanced(gl.POINTS,   2, gl.UNSIGNED_INT, 4*0, 1)`, [255, 10+1, 0, 255]);
-        fn(`gl.drawElementsInstanced(gl.POINTS,   1, gl.UNSIGNED_INT, 4*0, 2)`, [255, 10+0, 1, 255]);
-        fn(`gl.drawElementsInstanced(gl.POINTS,   2, gl.UNSIGNED_INT, 4*0, 2)`, [255, 10+1, 1, 255]);
-        fn(`gl.drawElementsInstanced(gl.POINTS,   2, gl.UNSIGNED_INT, 4*100, 2)`, [255, 100+10+1, 1, 255]);
-        fn(`gl.drawElementsInstanced(gl.POINTS, 245, gl.UNSIGNED_INT, 4*0, 255)`, [255, 10+244, 254, 255]);
-
-        // -
-
-        gl.useProgram(tri_prog);
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawArrays(gl.TRIANGLES,   0, 0*3)`, [0, 0, 0, 0]);
-        fn(`gl.drawArrays(gl.TRIANGLES,   0, 1*3)`, [255, 1*3-1, 0, 255]);
-        fn(`gl.drawArrays(gl.TRIANGLES,   0, 2*3)`, [255, 2*3-1, 0, 255]);
-        if (ERRATA.FIRST_ADDS_TO_INSTANCE) {
-            fn(`gl.drawArrays(gl.TRIANGLES,  90, 2*3)`, [255, 90+2*3-1, 90, 255]);
-        } else {
-            fn(`gl.drawArrays(gl.TRIANGLES,  90, 2*3)`, [255, 90+2*3-1, 0, 255]);
-        }
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawArraysInstanced(gl.TRIANGLES,   0, 0, 1)`, [0, 0, 0, 0]);
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawArraysInstanced(gl.TRIANGLES,   0, 1*3, 0)`, [0, 0, 0, 0]);
-
-        fn(`gl.drawArraysInstanced(gl.TRIANGLES,   0, 1*3, 1)`, [255, 1*3-1, 0, 255]);
-        fn(`gl.drawArraysInstanced(gl.TRIANGLES,   0, 2*3, 1)`, [255, 2*3-1, 0, 255]);
-        fn(`gl.drawArraysInstanced(gl.TRIANGLES,   0, 1*3, 2)`, [255, 1*3-1, 1, 255]);
-        fn(`gl.drawArraysInstanced(gl.TRIANGLES,   0, 2*3, 2)`, [255, 2*3-1, 1, 255]);
-        if (ERRATA.FIRST_ADDS_TO_INSTANCE) {
-            fn(`gl.drawArraysInstanced(gl.TRIANGLES, 90, 2*3, 2)`, [255, 90+2*3-1, 91, 255]);
-        } else {
-            fn(`gl.drawArraysInstanced(gl.TRIANGLES, 90, 2*3, 2)`, [255, 90+2*3-1, 1, 255]);
-        }
-
-        // -
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawElements(gl.TRIANGLES,   0*3, gl.UNSIGNED_INT, 4*0)`, [0, 0, 0, 0]);
-        fn(`gl.drawElements(gl.TRIANGLES,   1*3, gl.UNSIGNED_INT, 4*0)`, [255, 10+1*3-1, 0, 255]);
-        fn(`gl.drawElements(gl.TRIANGLES,   2*3, gl.UNSIGNED_INT, 4*0)`, [255, 10+2*3-1, 0, 255]);
-        fn(`gl.drawElements(gl.TRIANGLES,   2*3, gl.UNSIGNED_INT, 4*100)`, [255, 100+10+2*3-1, 0, 255]);
-
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawElementsInstanced(gl.TRIANGLES,   0*3, gl.UNSIGNED_INT, 4*0, 1)`, [0, 0, 0, 0]);
-        gl.clear(gl.COLOR_BUFFER_BIT);
-        fn(`gl.drawElementsInstanced(gl.TRIANGLES,   1*3, gl.UNSIGNED_INT, 4*0, 0)`, [0, 0, 0, 0]);
-
-        fn(`gl.drawElementsInstanced(gl.TRIANGLES,   1*3, gl.UNSIGNED_INT, 4*0, 1)`, [255, 10+1*3-1, 0, 255]);
-        fn(`gl.drawElementsInstanced(gl.TRIANGLES,   2*3, gl.UNSIGNED_INT, 4*0, 1)`, [255, 10+2*3-1, 0, 255]);
-        fn(`gl.drawElementsInstanced(gl.TRIANGLES,   1*3, gl.UNSIGNED_INT, 4*0, 2)`, [255, 10+1*3-1, 1, 255]);
-        fn(`gl.drawElementsInstanced(gl.TRIANGLES,   2*3, gl.UNSIGNED_INT, 4*0, 2)`, [255, 10+2*3-1, 1, 255]);
-        fn(`gl.drawElementsInstanced(gl.TRIANGLES,   2*3, gl.UNSIGNED_INT, 4*100, 2)`, [255, 100+10+2*3-1, 1, 255]);
-    }
-
-    finishTest();
-})();
-
-var successfullyParsed = true;
-</script>
-</body>
-</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/00_test_list.txt
index 17f8312e58..3639c10547 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/00_test_list.txt
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/00_test_list.txt
@@ -20,6 +20,7 @@ mipmap-fbo.html
 --min-version 2.0.1 origin-clean-conformance-offscreencanvas.html
 tex-3d-size-limit.html
 --min-version 2.0.1 tex-base-level-bug.html
+--min-version 2.0.1 tex-image-10bpc.html
 tex-image-and-sub-image-with-array-buffer-view-sub-source.html
 tex-image-with-bad-args.html
 tex-image-with-bad-args-from-dom-elements.html
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-10bpc.html b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-10bpc.html
new file mode 100644
index 0000000000..973a0ec0f5
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-10bpc.html
@@ -0,0 +1,66 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8" />
+<title>Ensure 10bpc image is not crushed to 8bpc in texImage2D</title>
+<link rel="stylesheet" href="../../../resources/js-test-style.css" />
+<script src="../../../js/js-test-pre.js"></script>
+<script src="../../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas id="example" width="24" height="24"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext("example", undefined, 2);
+var uniquePixels;
+
+// This is an 8x1, 10-bit-per-channel PNG (encoded as 16bpc).
+// The first pixel is black, and each next pixel is one brighter; approximately:
+// (0/1023,0,0), (1/1023,0,0), (2/1023,0,0), ..., (7/1023,0,0)
+const imgW = 8, imgH = 1;
+const imgURL = "../../../resources/red-gradient-8x1-10bit-untagged.png";
+
+const img = document.createElement("img");
+img.onload = () => {
+  const tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  const level = 0;
+  const internalformat = gl.RGB10_A2;
+  const border = 0;
+  const format = gl.RGBA;
+  const type = gl.UNSIGNED_INT_2_10_10_10_REV;
+  gl.texImage2D(gl.TEXTURE_2D, level, internalformat, imgW, imgH, border, format, type, img);
+
+  const fbo = gl.createFramebuffer();
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+  gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
+
+  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
+
+  const pixels = new Uint32Array(imgW * imgH);
+  gl.readPixels(0, 0, imgW, imgH, format, type, pixels);
+  uniquePixels = new Set(pixels);
+  // If the image was crushed to 8bpc, there will be 2-3 distinct values:
+  // (0/255,0,0), (1/255,0,0), and maybe (2/255,0,0) (depending on truncation vs rounding).
+  // If it wasn't, there should be 7-8.
+  // At time of writing, on Mac M1, Chrome gets 2 if it's crushed, and 7 if it's not.
+  shouldBeGreaterThanOrEqual("uniquePixels.size", "7", "there should be at least 7 distinct color values");
+
+  finishTest();
+};
+img.src = imgURL;
+
+var successfullyParsed = true;
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-with-bad-args-from-dom-elements.html b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-with-bad-args-from-dom-elements.html
index f1616e81d7..34ece05699 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-with-bad-args-from-dom-elements.html
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-image-with-bad-args-from-dom-elements.html
@@ -106,7 +106,6 @@ var tests = [
   { type: "video", src: "../../../resources/red-green.mp4", videoType: 'video/mp4; codecs="avc1.42E01E, mp4a.40.2"', run: testVideo },
   { type: "video", src: "../../../resources/red-green.bt601.vp9.webm", videoType: 'video/webm; codecs="vp9"', run: testVideo },
   { type: "video", src: "../../../resources/red-green.webmvp8.webm", videoType: 'video/webm; codecs="vp8, vorbis"', run: testVideo },
-  { type: "video", src: "../../../resources/red-green.theora.ogv", videoType: 'video/ogg; codecs="theora, vorbis"', run: testVideo },
 ];
 
 var testIndex = 0;
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-new-formats.html b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-new-formats.html
index df10edb4d3..760bc6bd19 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-new-formats.html
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/textures/misc/tex-new-formats.html
@@ -37,6 +37,7 @@ if (!gl) {
     testPassed("WebGL context exists");
 
     runTexFormatsTest();
+    runDepthStencilFormatTest();
 
     wtu.glErrorShouldBe(gl, gl.NO_ERROR, "there should be no errors");
 }
@@ -556,6 +557,35 @@ function runTexFormatsTest()
     });
 }
 
+function runDepthStencilFormatTest() {
+    debug("");
+    debug("Testing FLOAT_32_UNSIGNED_INT_24_8_REV with data");
+    const fb = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+
+    const tex2D = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, tex2D);
+    gl.texImage2D(gl.TEXTURE_2D, 0, gl.DEPTH32F_STENCIL8, 1, 1, 0, gl.DEPTH_STENCIL, gl.FLOAT_32_UNSIGNED_INT_24_8_REV, new Uint8Array(8));
+    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
+    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.TEXTURE_2D, tex2D, 0);
+    if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
+        testFailed("2D texture with invalid type was created");
+    } else {
+        testPassed("2D texture with invalid type was not created")
+    }
+
+    const tex3D = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D_ARRAY, tex3D);
+    gl.texImage3D(gl.TEXTURE_2D_ARRAY, 0, gl.DEPTH32F_STENCIL8, 1, 1, 1, 0, gl.DEPTH_STENCIL, gl.FLOAT_32_UNSIGNED_INT_24_8_REV, new Uint8Array(8));
+    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION);
+    gl.framebufferTextureLayer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, tex3D, 0, 0);
+    if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
+        testFailed("2D array texture with invalid type was created");
+    } else {
+        testPassed("2D array texture with invalid type was not created")
+    }
+}
+
 debug("");
 var successfullyParsed = true;
 </script>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/simultaneous_binding.html b/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/simultaneous_binding.html
index 228b4ab5cf..11d1eaa829 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/simultaneous_binding.html
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/simultaneous_binding.html
@@ -304,6 +304,17 @@ for (let genericBindPointValue of genericBindPointValues) {
   gl.copyBufferSubData(gl.COPY_READ_BUFFER, gl.COPY_WRITE_BUFFER, 0, 0, 1);
   wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "copyBufferSubData with double bound buffer");
 
+  debug("<hr/>Test that rejected operations do not change the bound buffer size");
+
+  gl.bindBuffer(gl.ARRAY_BUFFER, tfBuffer);
+  gl.bufferData(gl.ARRAY_BUFFER, 8, gl.STATIC_DRAW);
+  wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "bufferData with double bound buffer");
+
+  gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, null);
+  gl.bufferSubData(gl.ARRAY_BUFFER, 0, new Uint8Array(16));
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "bufferSubData should succeed");
+  gl.bindBuffer(gl.ARRAY_BUFFER, null);
+
   debug("<hr/>Test bufferData family with tf object unbound");
 
   gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, null);
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/transform_feedback.html b/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/transform_feedback.html
index 20256c6ace..16855453f0 100644
--- a/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/transform_feedback.html
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/transform_feedback/transform_feedback.html
@@ -64,6 +64,8 @@ if (!gl) {
     runUnboundDeleteTest();
     runBoundDeleteTest();
     runOneOutputFeedbackTest();
+    runUnchangedBufferBindingsTest();
+    runNoOutputsTest();
     // Must be the last test, since it's asynchronous and calls finishTest().
     runTwoOutputFeedbackTest();
 }
@@ -638,6 +640,70 @@ function runContextLostOneOutputFeedbackTest() {
     finishTest();
 }
 
+function runUnchangedBufferBindingsTest() {
+    debug("");
+    debug("Testing that buffer bindings cannot be changed while transform feedback is active");
+
+    program = wtu.setupTransformFeedbackProgram(
+        gl, [wtu.simpleVertexShader, wtu.simpleColorFragmentShader], ['gl_Position'], gl.INTERLEAVED_ATTRIBS);
+
+    tf = gl.createTransformFeedback();
+    gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, tf);
+
+    buf = gl.createBuffer();
+    gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 0, buf);
+
+    gl.beginTransformFeedback(gl.POINTS);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Transform feedback is active");
+
+    gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 0, gl.createBuffer());
+    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "Cannot change the bound buffer while transform feedback is active");
+    shouldBe("gl.getIndexedParameter(gl.TRANSFORM_FEEDBACK_BUFFER_BINDING, 0)", "buf");
+
+    gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 0, buf);
+    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "Cannot rebind the same buffer while transform feedback is active");
+
+    gl.bindBufferRange(gl.TRANSFORM_FEEDBACK_BUFFER, 0, gl.createBuffer(), 0, 64);
+    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "Cannot change the bound buffer while transform feedback is active");
+    shouldBe("gl.getIndexedParameter(gl.TRANSFORM_FEEDBACK_BUFFER_BINDING, 0)", "buf");
+
+    gl.bindBufferRange(gl.TRANSFORM_FEEDBACK_BUFFER, 0, buf, 0, 64);
+    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "Cannot rebind the same buffer while transform feedback is active");
+
+    gl.endTransformFeedback();
+    gl.deleteTransformFeedback(tf);
+    gl.deleteBuffer(buf);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "No extra errors after the test");
+}
+
+function runNoOutputsTest() {
+    debug("");
+    debug("Testing transform feedback with no varyings to record");
+
+    tf = gl.createTransformFeedback();
+    gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, tf);
+
+    buf = gl.createBuffer();
+    gl.bindBufferBase(gl.TRANSFORM_FEEDBACK_BUFFER, 0, buf);
+
+    for (const mode of ['SEPARATE_ATTRIBS', 'INTERLEAVED_ATTRIBS']) {
+        program = wtu.setupTransformFeedbackProgram(
+            gl, [wtu.simpleVertexShader, wtu.simpleColorFragmentShader], [], gl[mode]);
+
+        debug(`Testing with ${mode}`);
+        gl.beginTransformFeedback(gl.POINTS);
+        wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "beginTransformFeedback: No varyings to record");
+        gl.useProgram(null);
+        wtu.glErrorShouldBe(gl, gl.NO_ERROR, "useProgram: Transform feedback is not active");
+        gl.endTransformFeedback();
+        wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "endTransformFeedback: Transform feedback is not active");
+    }
+
+    gl.deleteTransformFeedback(tf);
+    gl.deleteBuffer(buf);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "No extra errors after the test");
+}
+
 debug("");
 </script>
 
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/00_test_list.txt
new file mode 100644
index 0000000000..d188fc30a6
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/00_test_list.txt
@@ -0,0 +1,12 @@
+--min-version 2.0.1 readpixels-16gb-wasm-memory.html
+--min-version 2.0.1 readpixels-4gb-wasm-memory.html
+--min-version 2.0.1 teximage2d-16gb-wasm-memory.html
+--min-version 2.0.1 teximage2d-4gb-wasm-memory.html
+--min-version 2.0.1 texsubimage2d-16gb-wasm-memory.html
+--min-version 2.0.1 texsubimage2d-4gb-wasm-memory.html
+--min-version 2.0.1 bufferdata-16gb-wasm-memory.html
+--min-version 2.0.1 bufferdata-4gb-wasm-memory.html
+--min-version 2.0.1 buffersubdata-16gb-wasm-memory.html
+--min-version 2.0.1 buffersubdata-4gb-wasm-memory.html
+--min-version 2.0.1 getbuffersubdata-16gb-wasm-memory.html
+--min-version 2.0.1 getbuffersubdata-4gb-wasm-memory.html
\ No newline at end of file
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-16gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-16gb-wasm-memory.html
new file mode 100644
index 0000000000..0dd21bf64f
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-16gb-wasm-memory.html
@@ -0,0 +1,51 @@
+<!--
+Copyright (c) 2024 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>bufferData test to Wasm Memory 16GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that bufferData can be called on WebAssembly Memory of 16GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 16 * 1024 * 1024 * 1024;
+let view = new Uint8Array(new WebAssembly.Memory({ index: 'i64', initial: SIZE / PAGE }).buffer);
+let expectedData = new Uint8Array([1, 2, 3, 4]);
+const length = expectedData.length;
+const offset = SIZE - length;
+view.set(expectedData, offset);
+
+let buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, view, gl.STATIC_DRAW, offset, length);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+let actualData = new Uint8Array(length);
+gl.getBufferSubData(gl.ARRAY_BUFFER, 0, actualData);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+for (let i = 0; i < length; i++) {
+  shouldBe(`actualData[${i}]`, `expectedData[${i}]`);
+}
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-4gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-4gb-wasm-memory.html
new file mode 100644
index 0000000000..2296c3a5ea
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/bufferdata-4gb-wasm-memory.html
@@ -0,0 +1,51 @@
+<!--
+Copyright (c) 2024 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>bufferData test to Wasm Memory 4GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that bufferData can be called on WebAssembly Memory of 4GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 4 * 1024 * 1024 * 1024 - PAGE;
+let view = new Uint8Array(new WebAssembly.Memory({ initial: SIZE / PAGE }).buffer);
+let expectedData = new Uint8Array([1, 2, 3, 4]);
+const length = expectedData.length;
+const offset = SIZE - length;
+view.set(expectedData, offset);
+
+let buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, view, gl.STATIC_DRAW, offset, length);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+let actualData = new Uint8Array(length);
+gl.getBufferSubData(gl.ARRAY_BUFFER, 0, actualData);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+for (let i = 0; i < length; i++) {
+  shouldBe(`actualData[${i}]`, `expectedData[${i}]`);
+}
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-16gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-16gb-wasm-memory.html
new file mode 100644
index 0000000000..08d6d1df50
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-16gb-wasm-memory.html
@@ -0,0 +1,52 @@
+<!--
+Copyright (c) 2024 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>bufferSubData test to Wasm Memory 16GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that bufferSubData can be called on WebAssembly Memory of 16GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 16 * 1024 * 1024 * 1024;
+let view = new Uint8Array(new WebAssembly.Memory({ index: 'i64', initial: SIZE / PAGE }).buffer);
+let expectedData = new Uint8Array([1, 2]);
+const length = expectedData.length;
+let srcOffset = SIZE - length;
+view.set(expectedData, srcOffset);
+const dstByteOffset = 4;
+
+let buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, 8, gl.STATIC_DRAW);
+gl.bufferSubData(gl.ARRAY_BUFFER, dstByteOffset, view, srcOffset, length);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+let actualData = new Uint8Array(length);
+gl.getBufferSubData(gl.ARRAY_BUFFER, dstByteOffset, actualData);
+for (let i = 0; i < length; i++) {
+  shouldBe(`actualData[${i}]`, `expectedData[${i}]`);
+}
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-4gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-4gb-wasm-memory.html
new file mode 100644
index 0000000000..2834a6901b
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/buffersubdata-4gb-wasm-memory.html
@@ -0,0 +1,52 @@
+<!--
+Copyright (c) 2024 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>bufferSubData test to Wasm Memory 4GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that bufferSubData can be called on WebAssembly Memory of 4GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 4 * 1024 * 1024 * 1024 - PAGE;
+let view = new Uint8Array(new WebAssembly.Memory({ initial: SIZE / PAGE }).buffer);
+let expectedData = new Uint8Array([1, 2]);
+const length = expectedData.length;
+let srcOffset = SIZE - length;
+view.set(expectedData, srcOffset);
+const dstByteOffset = 4;
+
+let buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, 8, gl.STATIC_DRAW);
+gl.bufferSubData(gl.ARRAY_BUFFER, dstByteOffset, view, srcOffset, length);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+let actualData = new Uint8Array(length);
+gl.getBufferSubData(gl.ARRAY_BUFFER, dstByteOffset, actualData);
+for (let i = 0; i < length; i++) {
+  shouldBe(`actualData[${i}]`, `expectedData[${i}]`);
+}
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-16gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-16gb-wasm-memory.html
new file mode 100644
index 0000000000..8390957b02
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-16gb-wasm-memory.html
@@ -0,0 +1,48 @@
+<!--
+Copyright (c) 2024 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>getBufferSubData test to Wasm Memory 16GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that getBufferSubData can be called on WebAssembly Memory of 16GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 16 * 1024 * 1024 * 1024;
+let view = new Uint8Array(new WebAssembly.Memory({ index: 'i64', initial: SIZE / PAGE }).buffer);
+let expectedData = new Uint8Array([1, 2, 3, 4]);
+
+let buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, expectedData, gl.STATIC_DRAW);
+
+const length = expectedData.length;
+const offset = SIZE - length;
+gl.getBufferSubData(gl.ARRAY_BUFFER, 0, view, offset, length);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+for (let i = 0; i < length; i++) {
+  shouldBe(`view[${i + offset}]`, `expectedData[${i}]`);
+}
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-4gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-4gb-wasm-memory.html
new file mode 100644
index 0000000000..09a336b753
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/getbuffersubdata-4gb-wasm-memory.html
@@ -0,0 +1,48 @@
+<!--
+Copyright (c) 2024 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>getBufferSubData test to Wasm Memory 4GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that getBufferSubData can be called on WebAssembly Memory of 4GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 4 * 1024 * 1024 * 1024 - PAGE;
+let view = new Uint8Array(new WebAssembly.Memory({ initial: SIZE / PAGE }).buffer);
+let expectedData = new Uint8Array([1, 2, 3, 4]);
+
+let buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, expectedData, gl.STATIC_DRAW);
+
+const length = expectedData.length;
+const offset = SIZE - length;
+gl.getBufferSubData(gl.ARRAY_BUFFER, 0, view, offset, length);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+for (let i = 0; i < length; i++) {
+  shouldBe(`view[${i + offset}]`, `expectedData[${i}]`);
+}
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-16gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-16gb-wasm-memory.html
new file mode 100644
index 0000000000..af74678dda
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-16gb-wasm-memory.html
@@ -0,0 +1,51 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>gl.readPixels() test to Wasm Memory 16GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("");
+debug("Tests that gl.readPixels() can be called on WebAssembly Memory of 16GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 16*1024*1024*1024;
+let view = new Uint8Array(new WebAssembly.Memory({ index: 'i64', initial: SIZE/PAGE }).buffer);
+
+// Clear the canvas to a specific color
+const expectedColor = [42, 84, 128, 255];
+gl.clearColor(expectedColor[0]/255.0, expectedColor[1]/255.0, expectedColor[2]/255.0, expectedColor[3]/255.0);
+gl.clear(gl.COLOR_BUFFER_BIT);
+
+// Test that gl.readPixels() can be called with a high offset to Memory
+const offset = SIZE - 4;
+view.set([0,0,0,0], offset); // For good measure, clear data at offset before reading
+gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, view, offset);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+let obtainedColor = view.subarray(offset, offset+4);
+shouldBe('obtainedColor[0]', 'expectedColor[0]');
+shouldBe('obtainedColor[1]', 'expectedColor[1]');
+shouldBe('obtainedColor[2]', 'expectedColor[2]');
+shouldBe('obtainedColor[3]', 'expectedColor[3]');
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-4gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-4gb-wasm-memory.html
new file mode 100644
index 0000000000..f97a3ccba0
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/readpixels-4gb-wasm-memory.html
@@ -0,0 +1,50 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>gl.readPixels() test to Wasm Memory 4GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that gl.readPixels() can be called on WebAssembly Memory of 4GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 4*1024*1024*1024 - PAGE; // when uint32_t size is max, we can only reach one page short of full 4GB
+let view = new Uint8Array(new WebAssembly.Memory({ initial: SIZE/PAGE }).buffer);
+
+// Clear the canvas to a specific color
+const expectedColor = [42, 84, 128, 255];
+gl.clearColor(expectedColor[0]/255.0, expectedColor[1]/255.0, expectedColor[2]/255.0, expectedColor[3]/255.0);
+gl.clear(gl.COLOR_BUFFER_BIT);
+
+// Test that gl.readPixels() can be called with a high offset to Memory
+const offset = SIZE - 4;
+view.set([0,0,0,0], offset); // For good measure, clear data at offset before reading
+gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, view, offset);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+let obtainedColor = view.subarray(offset, offset+4);
+shouldBe('obtainedColor[0]', 'expectedColor[0]');
+shouldBe('obtainedColor[1]', 'expectedColor[1]');
+shouldBe('obtainedColor[2]', 'expectedColor[2]');
+shouldBe('obtainedColor[3]', 'expectedColor[3]');
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-16gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-16gb-wasm-memory.html
new file mode 100644
index 0000000000..8ce5111953
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-16gb-wasm-memory.html
@@ -0,0 +1,85 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>gl.texImage2D() test to Wasm Memory 16GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that gl.texImage2D() can be called on WebAssembly Memory 16GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 16*1024*1024*1024;
+let view = new Uint8Array(new WebAssembly.Memory({ index: 'i64', initial: SIZE/PAGE }).buffer);
+
+function compileShader(type, src) {
+  let shader = gl.createShader(type);
+  gl.shaderSource(shader, src);
+  gl.compileShader(shader);
+  let log = gl.getShaderInfoLog(shader);
+  if (log) debug(log);
+  return shader;
+}
+
+function createProgram(vs, fs) {
+  let program = gl.createProgram();
+  gl.attachShader(program, vs);
+  gl.attachShader(program, fs);
+  gl.bindAttribLocation(program, 0, 'pos');
+  gl.linkProgram(program);
+  gl.useProgram(program);
+  return program;
+}
+
+let program = createProgram(
+  compileShader(gl.VERTEX_SHADER, `
+    varying vec2 uv;
+    attribute vec2 pos;
+    void main() { uv = pos; gl_Position = vec4(pos*2.0-vec2(1.0,1.0),0,1); }`),
+  compileShader(gl.FRAGMENT_SHADER, `
+    precision lowp float;
+    uniform sampler2D tex;
+    varying vec2 uv;
+    void main() { gl_FragColor = texture2D(tex,uv); }`));
+
+gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]), gl.STATIC_DRAW);
+gl.vertexAttribPointer(0, 2, gl.FLOAT, gl.FALSE, 0, 0);
+gl.enableVertexAttribArray(0);
+
+let texture = gl.createTexture();
+gl.bindTexture(gl.TEXTURE_2D, texture);
+
+// Test uploading an image
+const expectedColor = [42, 84, 128, 255];
+const offset = SIZE - 4;
+view.set(expectedColor, offset);
+gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, view, offset);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+// Test rendering with that image
+gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
+
+// Verify that we rendered what we expected
+wtu.checkCanvasRect(gl, 0, 0, 1, 1, expectedColor, "texImage2D produced expected color");
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-4gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-4gb-wasm-memory.html
new file mode 100644
index 0000000000..5d6897347d
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/teximage2d-4gb-wasm-memory.html
@@ -0,0 +1,85 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>gl.texImage2D() test to Wasm Memory 4GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that gl.texImage2D() can be called on WebAssembly Memory 4GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 4*1024*1024*1024 - PAGE; // when uint32_t size is max, we can only reach one page short of full 4GB
+let view = new Uint8Array(new WebAssembly.Memory({ initial: SIZE/PAGE }).buffer);
+
+function compileShader(type, src) {
+  let shader = gl.createShader(type);
+  gl.shaderSource(shader, src);
+  gl.compileShader(shader);
+  let log = gl.getShaderInfoLog(shader);
+  if (log) debug(log);
+  return shader;
+}
+
+function createProgram(vs, fs) {
+  let program = gl.createProgram();
+  gl.attachShader(program, vs);
+  gl.attachShader(program, fs);
+  gl.bindAttribLocation(program, 0, 'pos');
+  gl.linkProgram(program);
+  gl.useProgram(program);
+  return program;
+}
+
+let program = createProgram(
+  compileShader(gl.VERTEX_SHADER, `
+    varying vec2 uv;
+    attribute vec2 pos;
+    void main() { uv = pos; gl_Position = vec4(pos*2.0-vec2(1.0,1.0),0,1); }`),
+  compileShader(gl.FRAGMENT_SHADER, `
+    precision lowp float;
+    uniform sampler2D tex;
+    varying vec2 uv;
+    void main() { gl_FragColor = texture2D(tex,uv); }`));
+
+gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]), gl.STATIC_DRAW);
+gl.vertexAttribPointer(0, 2, gl.FLOAT, gl.FALSE, 0, 0);
+gl.enableVertexAttribArray(0);
+
+let texture = gl.createTexture();
+gl.bindTexture(gl.TEXTURE_2D, texture);
+
+// Test uploading an image
+const expectedColor = [42, 84, 128, 255];
+const offset = SIZE - 4;
+view.set(expectedColor, offset);
+gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, view, offset);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+// Test rendering with that image
+gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
+
+// Verify that we rendered what we expected
+wtu.checkCanvasRect(gl, 0, 0, 1, 1, expectedColor, "texImage2D produced expected color");
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-16gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-16gb-wasm-memory.html
new file mode 100644
index 0000000000..328d42ec49
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-16gb-wasm-memory.html
@@ -0,0 +1,86 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>gl.texSubImage2D() test to Wasm Memory 16GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that gl.texSubImage2D() can be called on WebAssembly Memory 16GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 16*1024*1024*1024;
+let view = new Uint8Array(new WebAssembly.Memory({ index: 'i64', initial: SIZE/PAGE }).buffer);
+
+function compileShader(type, src) {
+  let shader = gl.createShader(type);
+  gl.shaderSource(shader, src);
+  gl.compileShader(shader);
+  let log = gl.getShaderInfoLog(shader);
+  if (log) debug(log);
+  return shader;
+}
+
+function createProgram(vs, fs) {
+  let program = gl.createProgram();
+  gl.attachShader(program, vs);
+  gl.attachShader(program, fs);
+  gl.bindAttribLocation(program, 0, 'pos');
+  gl.linkProgram(program);
+  gl.useProgram(program);
+  return program;
+}
+
+let program = createProgram(
+  compileShader(gl.VERTEX_SHADER, `
+    varying vec2 uv;
+    attribute vec2 pos;
+    void main() { uv = pos; gl_Position = vec4(pos*2.0-vec2(1.0,1.0),0,1); }`),
+  compileShader(gl.FRAGMENT_SHADER, `
+    precision lowp float;
+    uniform sampler2D tex;
+    varying vec2 uv;
+    void main() { gl_FragColor = texture2D(tex,uv); }`));
+
+gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]), gl.STATIC_DRAW);
+gl.vertexAttribPointer(0, 2, gl.FLOAT, gl.FALSE, 0, 0);
+gl.enableVertexAttribArray(0);
+
+let texture = gl.createTexture();
+gl.bindTexture(gl.TEXTURE_2D, texture);
+
+// Test uploading an image
+const expectedColor = [42, 84, 128, 255];
+const offset = SIZE - 4;
+view.set(expectedColor, offset);
+gl.texStorage2D(gl.TEXTURE_2D, 1, gl.RGBA8, 1, 1);
+gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, view, offset);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+// Test rendering with that image
+gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
+
+// Verify that we rendered what we expected
+wtu.checkCanvasRect(gl, 0, 0, 1, 1, expectedColor, "texSubImage2D produced expected color");
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-4gb-wasm-memory.html b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-4gb-wasm-memory.html
new file mode 100644
index 0000000000..d7756629a0
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance2/wasm/texsubimage2d-4gb-wasm-memory.html
@@ -0,0 +1,86 @@
+<!--
+Copyright (c) 2023 The Khronos Group Inc.
+Use of this source code is governed by an MIT-style license that can be
+found in the LICENSE.txt file.
+-->
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>gl.texSubImage2D() test to Wasm Memory 4GB in size.</title>
+<link rel="stylesheet" href="../../resources/js-test-style.css"/>
+<script src="../../js/js-test-pre.js"></script>
+<script src="../../js/webgl-test-utils.js"> </script>
+</head>
+<body>
+<canvas id="canvas" width="2" height="2" style="width: 40px; height: 40px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description(document.title);
+debug("Tests that gl.texSubImage2D() can be called on WebAssembly Memory 4GB in size.");
+debug("");
+let wtu = WebGLTestUtils;
+let gl = wtu.create3DContext("canvas", undefined, 2);
+
+const PAGE = 65536;
+const SIZE = 4*1024*1024*1024 - PAGE; // when uint32_t size is max, we can only reach one page short of full 4GB
+let view = new Uint8Array(new WebAssembly.Memory({ initial: SIZE/PAGE }).buffer);
+
+function compileShader(type, src) {
+  let shader = gl.createShader(type);
+  gl.shaderSource(shader, src);
+  gl.compileShader(shader);
+  let log = gl.getShaderInfoLog(shader);
+  if (log) debug(log);
+  return shader;
+}
+
+function createProgram(vs, fs) {
+  let program = gl.createProgram();
+  gl.attachShader(program, vs);
+  gl.attachShader(program, fs);
+  gl.bindAttribLocation(program, 0, 'pos');
+  gl.linkProgram(program);
+  gl.useProgram(program);
+  return program;
+}
+
+let program = createProgram(
+  compileShader(gl.VERTEX_SHADER, `
+    varying vec2 uv;
+    attribute vec2 pos;
+    void main() { uv = pos; gl_Position = vec4(pos*2.0-vec2(1.0,1.0),0,1); }`),
+  compileShader(gl.FRAGMENT_SHADER, `
+    precision lowp float;
+    uniform sampler2D tex;
+    varying vec2 uv;
+    void main() { gl_FragColor = texture2D(tex,uv); }`));
+
+gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]), gl.STATIC_DRAW);
+gl.vertexAttribPointer(0, 2, gl.FLOAT, gl.FALSE, 0, 0);
+gl.enableVertexAttribArray(0);
+
+let texture = gl.createTexture();
+gl.bindTexture(gl.TEXTURE_2D, texture);
+
+// Test uploading an image
+const expectedColor = [42, 84, 128, 255];
+const offset = SIZE - 4;
+view.set(expectedColor, offset);
+gl.texStorage2D(gl.TEXTURE_2D, 1, gl.RGBA8, 1, 1);
+gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, view, offset);
+wtu.glErrorShouldBe(gl, gl.NO_ERROR);
+
+// Test rendering with that image
+gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
+
+// Verify that we rendered what we expected
+wtu.checkCanvasRect(gl, 0, 0, 1, 1, expectedColor, "texSubImage2D produced expected color");
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
-- 
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