From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 21:33:14 +0200
Subject: Adding upstream version 115.7.0esr.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../checkout/conformance/context/00_test_list.txt  |  21 +
 .../context/constants-and-properties.html          | 546 +++++++++++++++++++++
 ...ttribute-preserve-drawing-buffer-antialias.html | 143 ++++++
 .../context-attribute-preserve-drawing-buffer.html | 117 +++++
 ...t-attributes-alpha-depth-stencil-antialias.html | 281 +++++++++++
 .../context/context-creation-and-destruction.html  |  35 ++
 .../conformance/context/context-creation.html      |  35 ++
 .../context-eviction-with-garbage-collection.html  |  57 +++
 .../conformance/context/context-hidden-alpha.html  | 166 +++++++
 .../conformance/context/context-lost-restored.html | 287 +++++++++++
 .../checkout/conformance/context/context-lost.html | 379 ++++++++++++++
 .../context/context-no-alpha-fbo-with-alpha.html   |  77 +++
 .../context/context-release-upon-reload.html       |  72 +++
 .../context/context-release-with-workers.html      |  72 +++
 .../conformance/context/context-size-change.html   |  92 ++++
 .../conformance/context/context-type-test.html     |  53 ++
 .../context/deleted-object-behavior.html           | 237 +++++++++
 .../incorrect-context-object-behaviour.html        | 165 +++++++
 .../checkout/conformance/context/methods.html      | 178 +++++++
 .../conformance/context/premultiplyalpha-test.html | 251 ++++++++++
 .../context-release-child-with-worker.html         |  55 +++
 .../context-release-upon-reload-child.html         |  54 ++
 .../context/resources/context-release-worker.js    |   4 +
 .../user-defined-properties-on-context.html        |  49 ++
 .../conformance/context/zero-sized-canvas.html     |  59 +++
 25 files changed, 3485 insertions(+)
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/00_test_list.txt
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/constants-and-properties.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer-antialias.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-attributes-alpha-depth-stencil-antialias.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation-and-destruction.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-eviction-with-garbage-collection.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-hidden-alpha.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost-restored.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-no-alpha-fbo-with-alpha.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-upon-reload.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-with-workers.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-size-change.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/context-type-test.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/deleted-object-behavior.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/incorrect-context-object-behaviour.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/methods.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/premultiplyalpha-test.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-child-with-worker.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-upon-reload-child.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-worker.js
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/user-defined-properties-on-context.html
 create mode 100644 dom/canvas/test/webgl-conf/checkout/conformance/context/zero-sized-canvas.html

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

diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/00_test_list.txt b/dom/canvas/test/webgl-conf/checkout/conformance/context/00_test_list.txt
new file mode 100644
index 0000000000..f1acae5dfa
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/00_test_list.txt
@@ -0,0 +1,21 @@
+--max-version 1.9.9 constants-and-properties.html
+--min-version 1.0.2 context-attribute-preserve-drawing-buffer.html
+--min-version 1.0.4 context-attribute-preserve-drawing-buffer-antialias.html
+context-attributes-alpha-depth-stencil-antialias.html
+--min-version 1.0.4 context-size-change.html
+--min-version 1.0.4 context-no-alpha-fbo-with-alpha.html
+--min-version 1.0.2 --slow context-creation-and-destruction.html
+--min-version 1.0.3 --slow context-creation.html
+--min-version 1.0.3 --slow context-eviction-with-garbage-collection.html
+--min-version 1.0.3 context-hidden-alpha.html
+--min-version 1.0.2 context-release-upon-reload.html
+--min-version 1.0.2 context-release-with-workers.html
+context-lost-restored.html
+context-lost.html
+--max-version 1.9.9 context-type-test.html
+--min-version 1.0.4 deleted-object-behavior.html
+incorrect-context-object-behaviour.html
+--max-version 1.9.9 methods.html
+premultiplyalpha-test.html
+--min-version 1.0.4 user-defined-properties-on-context.html
+--min-version 1.0.4 zero-sized-canvas.html
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/constants-and-properties.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/constants-and-properties.html
new file mode 100644
index 0000000000..ccf128e11b
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/constants-and-properties.html
@@ -0,0 +1,546 @@
+<!--
+Copyright (c) 2019 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 Constants and Properties 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>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<canvas id="canvas" style="width: 50px; height: 50px;"> </canvas>
+<script>
+"use strict";
+description("This test ensures that the WebGL context has all the constants and (non-function) properties in the specification.");
+
+var constants = {
+    /* ClearBufferMask */
+DEPTH_BUFFER_BIT               : 0x00000100,
+STENCIL_BUFFER_BIT             : 0x00000400,
+COLOR_BUFFER_BIT               : 0x00004000,
+
+    /* BeginMode */
+POINTS                         : 0x0000,
+LINES                          : 0x0001,
+LINE_LOOP                      : 0x0002,
+LINE_STRIP                     : 0x0003,
+TRIANGLES                      : 0x0004,
+TRIANGLE_STRIP                 : 0x0005,
+TRIANGLE_FAN                   : 0x0006,
+
+    /* AlphaFunction (not supported in ES20) */
+    /*      NEVER */
+    /*      LESS */
+    /*      EQUAL */
+    /*      LEQUAL */
+    /*      GREATER */
+    /*      NOTEQUAL */
+    /*      GEQUAL */
+    /*      ALWAYS */
+
+    /* BlendingFactorDest */
+ZERO                           : 0,
+ONE                            : 1,
+SRC_COLOR                      : 0x0300,
+ONE_MINUS_SRC_COLOR            : 0x0301,
+SRC_ALPHA                      : 0x0302,
+ONE_MINUS_SRC_ALPHA            : 0x0303,
+DST_ALPHA                      : 0x0304,
+ONE_MINUS_DST_ALPHA            : 0x0305,
+
+    /* BlendingFactorSrc */
+    /*      ZERO */
+    /*      ONE */
+DST_COLOR                      : 0x0306,
+ONE_MINUS_DST_COLOR            : 0x0307,
+SRC_ALPHA_SATURATE             : 0x0308,
+    /*      SRC_ALPHA */
+    /*      ONE_MINUS_SRC_ALPHA */
+    /*      DST_ALPHA */
+    /*      ONE_MINUS_DST_ALPHA */
+
+    /* BlendEquationSeparate */
+FUNC_ADD                       : 0x8006,
+BLEND_EQUATION                 : 0x8009,
+BLEND_EQUATION_RGB             : 0x8009,   /* same as BLEND_EQUATION */
+BLEND_EQUATION_ALPHA           : 0x883D,
+
+    /* BlendSubtract */
+FUNC_SUBTRACT                  : 0x800A,
+FUNC_REVERSE_SUBTRACT          : 0x800B,
+
+    /* Separate Blend Functions */
+BLEND_DST_RGB                  : 0x80C8,
+BLEND_SRC_RGB                  : 0x80C9,
+BLEND_DST_ALPHA                : 0x80CA,
+BLEND_SRC_ALPHA                : 0x80CB,
+CONSTANT_COLOR                 : 0x8001,
+ONE_MINUS_CONSTANT_COLOR       : 0x8002,
+CONSTANT_ALPHA                 : 0x8003,
+ONE_MINUS_CONSTANT_ALPHA       : 0x8004,
+BLEND_COLOR                    : 0x8005,
+
+    /* Buffer Objects */
+ARRAY_BUFFER                   : 0x8892,
+ELEMENT_ARRAY_BUFFER           : 0x8893,
+ARRAY_BUFFER_BINDING           : 0x8894,
+ELEMENT_ARRAY_BUFFER_BINDING   : 0x8895,
+
+STREAM_DRAW                    : 0x88E0,
+STATIC_DRAW                    : 0x88E4,
+DYNAMIC_DRAW                   : 0x88E8,
+
+BUFFER_SIZE                    : 0x8764,
+BUFFER_USAGE                   : 0x8765,
+
+CURRENT_VERTEX_ATTRIB          : 0x8626,
+
+    /* CullFaceMode */
+FRONT                          : 0x0404,
+BACK                           : 0x0405,
+FRONT_AND_BACK                 : 0x0408,
+
+    /* DepthFunction */
+    /*      NEVER */
+    /*      LESS */
+    /*      EQUAL */
+    /*      LEQUAL */
+    /*      GREATER */
+    /*      NOTEQUAL */
+    /*      GEQUAL */
+    /*      ALWAYS */
+
+    /* EnableCap */
+    /* TEXTURE_2D */
+CULL_FACE                      : 0x0B44,
+BLEND                          : 0x0BE2,
+DITHER                         : 0x0BD0,
+STENCIL_TEST                   : 0x0B90,
+DEPTH_TEST                     : 0x0B71,
+SCISSOR_TEST                   : 0x0C11,
+POLYGON_OFFSET_FILL            : 0x8037,
+SAMPLE_ALPHA_TO_COVERAGE       : 0x809E,
+SAMPLE_COVERAGE                : 0x80A0,
+
+    /* ErrorCode */
+NO_ERROR                       : 0,
+INVALID_ENUM                   : 0x0500,
+INVALID_VALUE                  : 0x0501,
+INVALID_OPERATION              : 0x0502,
+OUT_OF_MEMORY                  : 0x0505,
+
+    /* FrontFaceDirection */
+CW                             : 0x0900,
+CCW                            : 0x0901,
+
+    /* GetPName */
+LINE_WIDTH                     : 0x0B21,
+ALIASED_POINT_SIZE_RANGE       : 0x846D,
+ALIASED_LINE_WIDTH_RANGE       : 0x846E,
+CULL_FACE_MODE                 : 0x0B45,
+FRONT_FACE                     : 0x0B46,
+DEPTH_RANGE                    : 0x0B70,
+DEPTH_WRITEMASK                : 0x0B72,
+DEPTH_CLEAR_VALUE              : 0x0B73,
+DEPTH_FUNC                     : 0x0B74,
+STENCIL_CLEAR_VALUE            : 0x0B91,
+STENCIL_FUNC                   : 0x0B92,
+STENCIL_FAIL                   : 0x0B94,
+STENCIL_PASS_DEPTH_FAIL        : 0x0B95,
+STENCIL_PASS_DEPTH_PASS        : 0x0B96,
+STENCIL_REF                    : 0x0B97,
+STENCIL_VALUE_MASK             : 0x0B93,
+STENCIL_WRITEMASK              : 0x0B98,
+STENCIL_BACK_FUNC              : 0x8800,
+STENCIL_BACK_FAIL              : 0x8801,
+STENCIL_BACK_PASS_DEPTH_FAIL   : 0x8802,
+STENCIL_BACK_PASS_DEPTH_PASS   : 0x8803,
+STENCIL_BACK_REF               : 0x8CA3,
+STENCIL_BACK_VALUE_MASK        : 0x8CA4,
+STENCIL_BACK_WRITEMASK         : 0x8CA5,
+VIEWPORT                       : 0x0BA2,
+SCISSOR_BOX                    : 0x0C10,
+    /*      SCISSOR_TEST */
+COLOR_CLEAR_VALUE              : 0x0C22,
+COLOR_WRITEMASK                : 0x0C23,
+UNPACK_ALIGNMENT               : 0x0CF5,
+PACK_ALIGNMENT                 : 0x0D05,
+MAX_TEXTURE_SIZE               : 0x0D33,
+MAX_VIEWPORT_DIMS              : 0x0D3A,
+SUBPIXEL_BITS                  : 0x0D50,
+RED_BITS                       : 0x0D52,
+GREEN_BITS                     : 0x0D53,
+BLUE_BITS                      : 0x0D54,
+ALPHA_BITS                     : 0x0D55,
+DEPTH_BITS                     : 0x0D56,
+STENCIL_BITS                   : 0x0D57,
+POLYGON_OFFSET_UNITS           : 0x2A00,
+    /*      POLYGON_OFFSET_FILL */
+POLYGON_OFFSET_FACTOR          : 0x8038,
+TEXTURE_BINDING_2D             : 0x8069,
+SAMPLE_BUFFERS                 : 0x80A8,
+SAMPLES                        : 0x80A9,
+SAMPLE_COVERAGE_VALUE          : 0x80AA,
+SAMPLE_COVERAGE_INVERT         : 0x80AB,
+
+    /* GetTextureParameter */
+    /*      TEXTURE_MAG_FILTER */
+    /*      TEXTURE_MIN_FILTER */
+    /*      TEXTURE_WRAP_S */
+    /*      TEXTURE_WRAP_T */
+
+COMPRESSED_TEXTURE_FORMATS     : 0x86A3,
+
+    /* HintMode */
+DONT_CARE                      : 0x1100,
+FASTEST                        : 0x1101,
+NICEST                         : 0x1102,
+
+    /* HintTarget */
+GENERATE_MIPMAP_HINT            : 0x8192,
+
+    /* DataType */
+BYTE                           : 0x1400,
+UNSIGNED_BYTE                  : 0x1401,
+SHORT                          : 0x1402,
+UNSIGNED_SHORT                 : 0x1403,
+INT                            : 0x1404,
+UNSIGNED_INT                   : 0x1405,
+FLOAT                          : 0x1406,
+
+    /* PixelFormat */
+DEPTH_COMPONENT                : 0x1902,
+ALPHA                          : 0x1906,
+RGB                            : 0x1907,
+RGBA                           : 0x1908,
+LUMINANCE                      : 0x1909,
+LUMINANCE_ALPHA                : 0x190A,
+
+    /* PixelType */
+    /*      UNSIGNED_BYTE */
+UNSIGNED_SHORT_4_4_4_4         : 0x8033,
+UNSIGNED_SHORT_5_5_5_1         : 0x8034,
+UNSIGNED_SHORT_5_6_5           : 0x8363,
+
+    /* Shaders */
+FRAGMENT_SHADER                  : 0x8B30,
+VERTEX_SHADER                    : 0x8B31,
+MAX_VERTEX_ATTRIBS               : 0x8869,
+MAX_VERTEX_UNIFORM_VECTORS       : 0x8DFB,
+MAX_VARYING_VECTORS              : 0x8DFC,
+MAX_COMBINED_TEXTURE_IMAGE_UNITS : 0x8B4D,
+MAX_VERTEX_TEXTURE_IMAGE_UNITS   : 0x8B4C,
+MAX_TEXTURE_IMAGE_UNITS          : 0x8872,
+MAX_FRAGMENT_UNIFORM_VECTORS     : 0x8DFD,
+SHADER_TYPE                      : 0x8B4F,
+DELETE_STATUS                    : 0x8B80,
+LINK_STATUS                      : 0x8B82,
+VALIDATE_STATUS                  : 0x8B83,
+ATTACHED_SHADERS                 : 0x8B85,
+ACTIVE_UNIFORMS                  : 0x8B86,
+ACTIVE_ATTRIBUTES                : 0x8B89,
+SHADING_LANGUAGE_VERSION         : 0x8B8C,
+CURRENT_PROGRAM                  : 0x8B8D,
+
+    /* StencilFunction */
+NEVER                          : 0x0200,
+LESS                           : 0x0201,
+EQUAL                          : 0x0202,
+LEQUAL                         : 0x0203,
+GREATER                        : 0x0204,
+NOTEQUAL                       : 0x0205,
+GEQUAL                         : 0x0206,
+ALWAYS                         : 0x0207,
+
+    /* StencilOp */
+    /*      ZERO */
+KEEP                           : 0x1E00,
+REPLACE                        : 0x1E01,
+INCR                           : 0x1E02,
+DECR                           : 0x1E03,
+INVERT                         : 0x150A,
+INCR_WRAP                      : 0x8507,
+DECR_WRAP                      : 0x8508,
+
+    /* StringName */
+VENDOR                         : 0x1F00,
+RENDERER                       : 0x1F01,
+VERSION                        : 0x1F02,
+
+    /* TextureMagFilter */
+NEAREST                        : 0x2600,
+LINEAR                         : 0x2601,
+
+    /* TextureMinFilter */
+    /*      NEAREST */
+    /*      LINEAR */
+NEAREST_MIPMAP_NEAREST         : 0x2700,
+LINEAR_MIPMAP_NEAREST          : 0x2701,
+NEAREST_MIPMAP_LINEAR          : 0x2702,
+LINEAR_MIPMAP_LINEAR           : 0x2703,
+
+    /* TextureParameterName */
+TEXTURE_MAG_FILTER             : 0x2800,
+TEXTURE_MIN_FILTER             : 0x2801,
+TEXTURE_WRAP_S                 : 0x2802,
+TEXTURE_WRAP_T                 : 0x2803,
+
+    /* TextureTarget */
+TEXTURE_2D                     : 0x0DE1,
+TEXTURE                        : 0x1702,
+
+TEXTURE_CUBE_MAP               : 0x8513,
+TEXTURE_BINDING_CUBE_MAP       : 0x8514,
+TEXTURE_CUBE_MAP_POSITIVE_X    : 0x8515,
+TEXTURE_CUBE_MAP_NEGATIVE_X    : 0x8516,
+TEXTURE_CUBE_MAP_POSITIVE_Y    : 0x8517,
+TEXTURE_CUBE_MAP_NEGATIVE_Y    : 0x8518,
+TEXTURE_CUBE_MAP_POSITIVE_Z    : 0x8519,
+TEXTURE_CUBE_MAP_NEGATIVE_Z    : 0x851A,
+MAX_CUBE_MAP_TEXTURE_SIZE      : 0x851C,
+
+    /* TextureUnit */
+TEXTURE0                       : 0x84C0,
+TEXTURE1                       : 0x84C1,
+TEXTURE2                       : 0x84C2,
+TEXTURE3                       : 0x84C3,
+TEXTURE4                       : 0x84C4,
+TEXTURE5                       : 0x84C5,
+TEXTURE6                       : 0x84C6,
+TEXTURE7                       : 0x84C7,
+TEXTURE8                       : 0x84C8,
+TEXTURE9                       : 0x84C9,
+TEXTURE10                      : 0x84CA,
+TEXTURE11                      : 0x84CB,
+TEXTURE12                      : 0x84CC,
+TEXTURE13                      : 0x84CD,
+TEXTURE14                      : 0x84CE,
+TEXTURE15                      : 0x84CF,
+TEXTURE16                      : 0x84D0,
+TEXTURE17                      : 0x84D1,
+TEXTURE18                      : 0x84D2,
+TEXTURE19                      : 0x84D3,
+TEXTURE20                      : 0x84D4,
+TEXTURE21                      : 0x84D5,
+TEXTURE22                      : 0x84D6,
+TEXTURE23                      : 0x84D7,
+TEXTURE24                      : 0x84D8,
+TEXTURE25                      : 0x84D9,
+TEXTURE26                      : 0x84DA,
+TEXTURE27                      : 0x84DB,
+TEXTURE28                      : 0x84DC,
+TEXTURE29                      : 0x84DD,
+TEXTURE30                      : 0x84DE,
+TEXTURE31                      : 0x84DF,
+ACTIVE_TEXTURE                 : 0x84E0,
+
+    /* TextureWrapMode */
+REPEAT                         : 0x2901,
+CLAMP_TO_EDGE                  : 0x812F,
+MIRRORED_REPEAT                : 0x8370,
+
+    /* Uniform Types */
+FLOAT_VEC2                     : 0x8B50,
+FLOAT_VEC3                     : 0x8B51,
+FLOAT_VEC4                     : 0x8B52,
+INT_VEC2                       : 0x8B53,
+INT_VEC3                       : 0x8B54,
+INT_VEC4                       : 0x8B55,
+BOOL                           : 0x8B56,
+BOOL_VEC2                      : 0x8B57,
+BOOL_VEC3                      : 0x8B58,
+BOOL_VEC4                      : 0x8B59,
+FLOAT_MAT2                     : 0x8B5A,
+FLOAT_MAT3                     : 0x8B5B,
+FLOAT_MAT4                     : 0x8B5C,
+SAMPLER_2D                     : 0x8B5E,
+SAMPLER_CUBE                   : 0x8B60,
+
+    /* Vertex Arrays */
+VERTEX_ATTRIB_ARRAY_ENABLED        : 0x8622,
+VERTEX_ATTRIB_ARRAY_SIZE           : 0x8623,
+VERTEX_ATTRIB_ARRAY_STRIDE         : 0x8624,
+VERTEX_ATTRIB_ARRAY_TYPE           : 0x8625,
+VERTEX_ATTRIB_ARRAY_NORMALIZED     : 0x886A,
+VERTEX_ATTRIB_ARRAY_POINTER        : 0x8645,
+VERTEX_ATTRIB_ARRAY_BUFFER_BINDING : 0x889F,
+
+    /* Read Format */
+IMPLEMENTATION_COLOR_READ_TYPE   : 0x8B9A,
+IMPLEMENTATION_COLOR_READ_FORMAT : 0x8B9B,
+
+    /* Shader Source */
+COMPILE_STATUS                 : 0x8B81,
+
+    /* Shader Precision-Specified Types */
+LOW_FLOAT                      : 0x8DF0,
+MEDIUM_FLOAT                   : 0x8DF1,
+HIGH_FLOAT                     : 0x8DF2,
+LOW_INT                        : 0x8DF3,
+MEDIUM_INT                     : 0x8DF4,
+HIGH_INT                       : 0x8DF5,
+
+    /* Framebuffer Object. */
+FRAMEBUFFER                    : 0x8D40,
+RENDERBUFFER                   : 0x8D41,
+
+RGBA4                          : 0x8056,
+RGB5_A1                        : 0x8057,
+RGB565                         : 0x8D62,
+DEPTH_COMPONENT16              : 0x81A5,
+STENCIL_INDEX8                 : 0x8D48,
+DEPTH_STENCIL                  : 0x84F9,
+
+RENDERBUFFER_WIDTH             : 0x8D42,
+RENDERBUFFER_HEIGHT            : 0x8D43,
+RENDERBUFFER_INTERNAL_FORMAT   : 0x8D44,
+RENDERBUFFER_RED_SIZE          : 0x8D50,
+RENDERBUFFER_GREEN_SIZE        : 0x8D51,
+RENDERBUFFER_BLUE_SIZE         : 0x8D52,
+RENDERBUFFER_ALPHA_SIZE        : 0x8D53,
+RENDERBUFFER_DEPTH_SIZE        : 0x8D54,
+RENDERBUFFER_STENCIL_SIZE      : 0x8D55,
+
+FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE           : 0x8CD0,
+FRAMEBUFFER_ATTACHMENT_OBJECT_NAME           : 0x8CD1,
+FRAMEBUFFER_ATTACHMENT_TEXTURE_LEVEL         : 0x8CD2,
+FRAMEBUFFER_ATTACHMENT_TEXTURE_CUBE_MAP_FACE : 0x8CD3,
+
+COLOR_ATTACHMENT0              : 0x8CE0,
+DEPTH_ATTACHMENT               : 0x8D00,
+STENCIL_ATTACHMENT             : 0x8D20,
+DEPTH_STENCIL_ATTACHMENT       : 0x821A,
+
+NONE                           : 0,
+
+FRAMEBUFFER_COMPLETE                      : 0x8CD5,
+FRAMEBUFFER_INCOMPLETE_ATTACHMENT         : 0x8CD6,
+FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT : 0x8CD7,
+FRAMEBUFFER_INCOMPLETE_DIMENSIONS         : 0x8CD9,
+FRAMEBUFFER_UNSUPPORTED                   : 0x8CDD,
+
+FRAMEBUFFER_BINDING            : 0x8CA6,
+RENDERBUFFER_BINDING           : 0x8CA7,
+MAX_RENDERBUFFER_SIZE          : 0x84E8,
+
+INVALID_FRAMEBUFFER_OPERATION  : 0x0506,
+
+/* WebGL-specific enums */
+UNPACK_FLIP_Y_WEBGL                : 0x9240,
+UNPACK_PREMULTIPLY_ALPHA_WEBGL     : 0x9241,
+CONTEXT_LOST_WEBGL                 : 0x9242,
+UNPACK_COLORSPACE_CONVERSION_WEBGL : 0x9243,
+BROWSER_DEFAULT_WEBGL              : 0x9244
+};
+
+// Other non-function properties on the WebGL object
+var otherProperties = {
+drawingBufferWidth      : "number",
+drawingBufferHeight     : "number",
+drawingBufferColorSpace : "string",
+unpackColorSpace        : "string",
+canvas                  : "implementation-dependent"
+};
+
+// Properties to be ignored (as a list of strings) because they were
+// added in versions of the spec that are backward-compatible with
+// this version
+var ignoredProperties = [
+];
+
+// Constants removed from the WebGL spec compared to ES 2.0
+var removedConstants = {
+NUM_COMPRESSED_TEXTURE_FORMATS : 0x86A2,
+FIXED                          : 0x140C,
+ACTIVE_UNIFORM_MAX_LENGTH      : 0x8B87,
+ACTIVE_ATTRIBUTE_MAX_LENGTH    : 0x8B8A,
+EXTENSIONS                     : 0x1F03,
+INFO_LOG_LENGTH                : 0x8B84,
+SHADER_SOURCE_LENGTH           : 0x8B88,
+SHADER_COMPILER                : 0x8DFA,
+SHADER_BINARY_FORMATS          : 0x8DF8,
+NUM_SHADER_BINARY_FORMATS      : 0x8DF9,
+};
+
+function assertProperty(v, p) {
+  if (p in v) {
+    return true;
+  } else {
+    testFailed("Property does not exist: " + p)
+    return false;
+  }
+}
+
+function assertNoProperty(v, p) {
+  if (p in v) {
+    testFailed("Property is defined and should not be: " + p)
+    return false;
+  } else {
+    return true;
+  }
+}
+
+function assertMsg_(bool, msg) {
+  if (!bool) // show only failures to avoid spamming result list
+    assertMsg(bool, msg);
+  return bool;
+}
+
+debug("");
+debug("Canvas.getContext");
+
+var canvas = document.getElementById("canvas");
+var wtu = WebGLTestUtils;
+var gl = wtu.create3DContext(canvas);
+var passed = true;
+for (var i in constants) {
+  var r = assertProperty(gl, i) && assertMsg_(gl[i] == constants[i], "Property "+i+" value test "+gl[i]+" == "+constants[i]);
+  passed = passed && r;
+}
+if (passed) {
+  testPassed("All WebGL constants found to have correct values.");
+}
+passed = true;
+for (var i in removedConstants) {
+  var r = assertNoProperty(gl, i);
+  passed = passed && r;
+}
+if (passed) {
+  testPassed("All constants removed from WebGL spec were absent from WebGL context.");
+}
+var extended = false;
+for (var i in gl) {
+  if (constants[i] !== undefined) {
+    // OK; known constant
+  } else if (ignoredProperties.indexOf(i) != -1) {
+    // OK; constant that should be ignored because it was added in a later version of the spec
+  } else if (otherProperties[i] !== undefined &&
+             (otherProperties[i] == "implementation-dependent" || typeof gl[i] == otherProperties[i])) {
+    // OK; known property of known type
+  } else if (typeof gl[i] != "function" && removedConstants[i] === undefined) {
+    if (!extended) {
+      extended = true;
+      testFailed("Also found the following extra properties:");
+    }
+    testFailed(i);
+  }
+}
+
+if (!extended) {
+  testPassed("No extra properties found on WebGL context.");
+}
+
+debug("");
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer-antialias.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer-antialias.html
new file mode 100644
index 0000000000..fa8d9937db
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer-antialias.html
@@ -0,0 +1,143 @@
+<!--
+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="canvas" width="128" height="64" style="width: 32px; height: 32px;"></canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+
+const wtu = WebGLTestUtils;
+description(' Test drawingbuffer is preserved when drawing');
+
+const waitForComposite = () => new Promise(resolve => wtu.waitForComposite(resolve));
+const gl = wtu.create3DContext("canvas", {
+  preserveDrawingBuffer: true,
+  antialias: true,
+});
+console.log(gl.getContextAttributes());
+const w = 128;
+const h = 64;
+
+if (!gl) {
+    testFailed('canvas.getContext() failed');
+} else {
+    gl.viewport(0, 0, w, h);
+    runTest(gl, 4);
+}
+
+async function runTest(gl, sampleCount) {
+    const vs = `
+    attribute vec4 position;
+    uniform mat4 mat;
+
+    void main() {
+      gl_Position = mat * position;
+    }
+    `;
+
+    const fs = `
+    precision mediump float;
+    uniform vec4 color;
+    void main() {
+      gl_FragColor = color;
+    }
+    `;
+
+    const positionLoc = 0;  // hard coded in shaders so they match
+    const buf = gl.createBuffer();
+    gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
+      0, 0,
+      1, 0,
+      0, 1,
+      0, 1,
+      1, 0,
+      1, 1,
+    ]), gl.STATIC_DRAW);
+    gl.enableVertexAttribArray(positionLoc);
+    gl.vertexAttribPointer(positionLoc, 2, gl.FLOAT, false, 0, 0);
+
+    const program = wtu.setupProgram(gl, [vs, fs]);
+
+    const colorLoc = gl.getUniformLocation(program, 'color');
+    const matLoc = gl.getUniformLocation(program, 'mat');
+
+    gl.useProgram(program);
+
+    const draw = (color, mat) => {
+      gl.uniform4fv(colorLoc, color);
+      gl.uniformMatrix4fv(matLoc, false, mat);
+      gl.drawArrays(gl.TRIANGLES, 0, 6);
+    };
+
+    const f32Red    = [1, 0, 0, 1];
+    const f32Green  = [0, 1, 0, 1];
+    const f32Gray   = [0.5, 0.5, 0.5, 1];
+
+    const u8Red         = [255,   0,   0, 255];
+    const u8Green       = [  0, 255,   0, 255];
+    const u8LightRed    = [255, 128, 128, 255];
+    const u8LightGreen  = [128, 255, 128, 255];
+
+    draw(f32Red, [
+      2, 0, 0, 0,
+      0, 2, 0, 0,
+      0, 0, 1, 0,
+      -1, -1, 0, 1,
+    ]);
+    await waitForComposite();
+
+    draw(f32Green, [
+      1, 0, 0, 0,
+      0, 2, 0, 0,
+      0, 0, 1, 0,
+      0, -1, 0, 1,
+    ]);
+    await waitForComposite();
+
+    gl.enable(gl.BLEND);
+    gl.blendFunc(gl.ONE, gl.ONE);
+    draw(f32Gray, [
+      1, 0, 0, 0,
+      0, 2, 0, 0,
+      0, 0, 1, 0,
+      -0.5, -1, 0, 1,
+    ]);
+    gl.disable(gl.BLEND);
+    await waitForComposite();
+
+    /*
+       expected
+       +-----+-------+---------+--------+
+       | red | ltRed | ltGreen | green  |
+       +-----+-------+---------+--------+
+      0,0
+    */
+
+    const tolerance = 2; // For multisampling resolution differences between GPUs
+    wtu.checkCanvasRect(gl, 0, 0, w / 4, h , u8Red, 'left edge', tolerance)
+    wtu.checkCanvasRect(gl, w * 3 / 4, 0, w / 4, h, u8Green, 'right edge', tolerance);
+    wtu.checkCanvasRect(gl, w / 4, 0, w / 4, h, u8LightRed, 'left of center', tolerance);
+    wtu.checkCanvasRect(gl, w / 2, 0, w / 4, h, u8LightGreen, 'right of center', tolerance);
+
+    finishTest();
+}
+
+var successfullyParsed = true;
+shouldBeTrue("successfullyParsed");
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer.html
new file mode 100644
index 0000000000..7a023996fb
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attribute-preserve-drawing-buffer.html
@@ -0,0 +1,117 @@
+<!--
+Copyright (c) 2019 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>
+<style>
+.pattern {
+  white-space: nowrap;
+  display: inline-block;
+}
+canvas {
+  width:10px;
+  height:10px;
+}
+.square {
+  display:inline-block;
+  width:10px;
+  height:10px;
+  background-color:red;
+}
+</style>
+<script>
+"use strict";
+var wtu = WebGLTestUtils;
+function checkResult(ctx1, ctx2, preserve) {
+  var imgData1 = ctx1.getImageData(0,0,1,1);
+  var imgData2 = ctx2.getImageData(0,0,1,1);
+  var correct1 = [255,0,0,255];
+  var correct2 = preserve ? [255,0,0,255] : [0,0,0,255];
+  var ok1 = true;
+  var ok2 = true;
+  for (var p = 0; p < 4; ++p) {
+    if (imgData1.data[p] != correct1[p])
+      ok1 = false;
+    if (imgData2.data[p] != correct2[p])
+      ok2 = false;
+  }
+  if (ok1 && ok2)
+    testPassed('Rendered ok with preserveDrawingBuffer ' + preserve +'.');
+  else
+    testFailed('Did not render ok with preserveDrawingBuffer ' + preserve + '.');
+  if (preserve) {
+    finishTest()
+  } else {
+    runTest(true);
+  }
+}
+
+function runTest(preserve) {
+  var c1 = document.getElementById('c' + (preserve * 3 + 1));
+  var c2 = document.getElementById('c' + (preserve * 3 + 2));
+  var c3 = document.getElementById('c' + (preserve * 3 + 3));
+  var ctx1 = c1.getContext('2d');
+  var ctx2 = c2.getContext('2d');
+  var gl = wtu.create3DContext(c3, { alpha:false, preserveDrawingBuffer:preserve });
+  if (!gl) {
+    testFailed("context does not exist");
+    if (preserve) {
+      finishTest()
+    } else {
+      runTest(true);
+    }
+    return;
+  }
+  gl.clearColor(1, 0, 0, 1);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+  ctx1.drawImage(c3, 0, 0);
+  wtu.waitForComposite(function() {
+    ctx2.drawImage(c3, 0, 0);
+    checkResult(ctx1, ctx2, preserve);
+  });
+}
+</script>
+</head>
+<body>
+<div class="pattern">
+  <canvas id='c1'></canvas>
+  <canvas id='c2'></canvas>
+  <canvas id='c3'></canvas>
+</div>
+<span>should look like</span>
+<div class="pattern">
+  <div class='square'></div>
+  <div class='square' style='background-color:black'></div>
+  <div class='square'></div>
+</div>
+<hr />
+<div class="pattern">
+  <canvas id='c4'></canvas>
+  <canvas id='c5'></canvas>
+  <canvas id='c6'></canvas>
+</div>
+<span>should look like</span>
+<div class="pattern">
+  <div class='square'></div>
+  <div class='square'></div>
+  <div class='square'></div>
+</div>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description('Verify that preserveDrawingBuffer attribute is honored.');
+runTest(false);
+var successfullyParsed = true;
+shouldBeTrue("successfullyParsed");
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attributes-alpha-depth-stencil-antialias.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attributes-alpha-depth-stencil-antialias.html
new file mode 100644
index 0000000000..40f46a744a
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-attributes-alpha-depth-stencil-antialias.html
@@ -0,0 +1,281 @@
+<!--
+Copyright (c) 2019 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>
+<script id="vshader" type="x-shader/x-vertex">
+attribute vec3 pos;
+attribute vec4 colorIn;
+varying vec4 color;
+
+void main()
+{
+    color = colorIn;
+    gl_Position = vec4(pos.xyz, 1.0);
+}
+</script>
+
+<script id="fshader" type="x-shader/x-fragment">
+precision mediump float;
+
+varying vec4 color;
+
+void main()
+{
+    gl_FragColor = color;
+}
+</script>
+
+<script>
+"use strict";
+
+// These four declarations need to be global for "shouldBe" to see them
+var wtu = WebGLTestUtils;
+var gl;
+var contextAttribs = null;
+var redChannels = [0, 0, 0];
+var correctColor = null;
+var framebuffer;
+var fbHasColor;
+var fbHasDepth;
+var fbHasStencil;
+var contextVersion = wtu.getDefault3DContextVersion();
+
+function init()
+{
+    description('Verify WebGLContextAttributes are working as specified, including alpha, depth, stencil, antialias, but not premultipliedAlpha');
+
+    runTest();
+}
+
+var vertices = new Float32Array([
+    1.0, 1.0, 0.0,
+    -1.0, 1.0, 0.0,
+    -1.0, -1.0, 0.0,
+    1.0, 1.0, 0.0,
+    -1.0, -1.0, 0.0,
+    1.0, -1.0, 0.0]);
+
+var colors = new Uint8Array([
+    255, 0, 0, 255,
+    255, 0, 0, 255,
+    255, 0, 0, 255,
+    255, 0, 0, 255,
+    255, 0, 0, 255,
+    255, 0, 0, 255]);
+
+
+function getWebGL(canvasWidth, canvasHeight, contextAttribs, clearColor, clearDepth, clearStencil)
+{
+    var canvas = document.createElement("canvas");
+    if (!canvas)
+        return null;
+    canvas.width = canvasWidth;
+    canvas.height = canvasHeight;
+
+    gl = wtu.create3DContext(canvas, contextAttribs, contextVersion);
+    if (!gl)
+        return null;
+
+    var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["pos", "colorIn"]);
+    if (!program)
+        return null;
+
+    gl.enable(gl.DEPTH_TEST);
+    gl.enable(gl.STENCIL_TEST);
+
+    gl.clearColor(clearColor[0], clearColor[1], clearColor[2], clearColor[3]);
+    gl.clearDepth(clearDepth);
+    gl.clearStencil(clearStencil);
+    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
+
+    framebuffer = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+    var texture = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, texture);
+    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.canvas.width, gl.canvas.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
+    fbHasStencil = false;
+    fbHasDepth = false;
+    fbHasColor = gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE;
+    if (fbHasColor) {
+      var depthStencil = gl.createRenderbuffer();
+      gl.bindRenderbuffer(gl.RENDERBUFFER, depthStencil);
+      gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_STENCIL, gl.canvas.width, gl.canvas.height);
+      gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthStencil);
+      fbHasDepth = gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE;
+      if (!fbHasDepth) {
+        gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, null);
+        shouldBe('gl.checkFramebufferStatus(gl.FRAMEBUFFER)', 'gl.FRAMEBUFFER_COMPLETE');
+      } else {
+        fbHasStencil = true;
+      }
+    }
+    gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+
+    var colorOffset = vertices.byteLength;
+    var vbo = gl.createBuffer();
+    gl.bindBuffer(gl.ARRAY_BUFFER, vbo);
+    gl.bufferData(gl.ARRAY_BUFFER, colorOffset + colors.byteLength, gl.STATIC_DRAW);
+    gl.bufferSubData(gl.ARRAY_BUFFER, 0, vertices);
+    gl.bufferSubData(gl.ARRAY_BUFFER, colorOffset, colors);
+    gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);
+    gl.enableVertexAttribArray(0);
+    gl.vertexAttribPointer(1, 4, gl.UNSIGNED_BYTE, true, 0, colorOffset);
+    gl.enableVertexAttribArray(1);
+
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+    return gl;
+}
+
+function draw(gl, verticesCount)
+{
+    verticesCount = verticesCount || vertices.length / 3;
+    gl.drawArrays(gl.TRIANGLES, 0, verticesCount);
+}
+
+function checkDraw(hasAlpha, hasStencil, hasDepth, hasAntialias)
+{
+    let red = [255, 0, 0, 255 ];
+    let black = [0, 0, 0, hasAlpha ? 0 : 255 ];
+    debug(`Testing that stencil ${ hasStencil ? 'affects': 'does not affect'} the rendering.`);
+    gl.stencilFunc(gl.NEVER, 1, 1);
+    gl.stencilOp(gl.KEEP, gl.KEEP, gl.KEEP);
+    draw(gl);
+    correctColor = hasStencil ? black : red;
+    wtu.checkCanvas(gl, correctColor)
+    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
+    wtu.checkCanvas(gl, black);
+    gl.stencilFunc(gl.ALWAYS, 1, 1);
+
+    debug(`Testing that depth ${ hasDepth ? 'affects': 'does not affect'} the rendering.`);
+    gl.depthFunc(gl.NEVER);
+    draw(gl);
+    correctColor = hasDepth ? black : red;
+    wtu.checkCanvas(gl, correctColor);
+    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
+    wtu.checkCanvas(gl, black);
+    gl.depthFunc(gl.ALWAYS);
+
+    debug(`Testing that rendering is ${hasAntialias ? 'antialiased' : 'aliased'}.`);
+    draw(gl, 3);
+    let N = 2;
+    let buf = new Uint8Array(N * N * 4);
+    gl.readPixels(0, 0, N, N, gl.RGBA, gl.UNSIGNED_BYTE, buf);
+    redChannels[0] = buf[4 * (N + 1)]; // (1, 1)
+    redChannels[1] = buf[4 * N * (N - 1)]; // left top
+    redChannels[2] = buf[4 * (N - 1)]; // right bottom
+    shouldBe("redChannels[1]", "255");
+    shouldBe("redChannels[2]", "0");
+    if (hasAntialias) {
+        shouldNotBe("redChannels[0]", "255");
+        shouldNotBe("redChannels[0]", "0");
+    } else {
+        shouldBeTrue("redChannels[0] == 255 || redChannels[0] == 0");
+    }
+    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
+    wtu.checkCanvas(gl, black);
+
+    debug("Testing that rendering works.");
+    draw(gl);
+    wtu.checkCanvas(gl, red);
+    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
+    wtu.checkCanvas(gl, black);
+}
+
+function testDefault()
+{
+    debug("Testing default attributes: { stencil:false }");
+    shouldBeNonNull("gl = getWebGL(1, 1, null, [ 0, 0, 0, 0 ], 1, 0)");
+    shouldBeFalse("gl.getContextAttributes().stencil");
+    shouldBe("gl.getParameter(gl.STENCIL_BITS)", "0");
+}
+
+function testAttributesAffectContext(alpha, stencil, depth, antialias)
+{
+    shouldBeNonNull(`gl = getWebGL(2, 2, { depth: ${depth}, stencil: ${stencil}, antialias: ${antialias}, alpha: ${alpha} }, [ 0, 0, 0, 0 ], 1, 0)`);
+    shouldBeNonNull("contextAttribs = gl.getContextAttributes()");
+
+    shouldBeGreaterThanOrEqual("gl.getParameter(gl.RED_BITS)", "8");
+    shouldBeGreaterThanOrEqual("gl.getParameter(gl.GREEN_BITS)", "8");
+    shouldBeGreaterThanOrEqual("gl.getParameter(gl.BLUE_BITS)", "8");
+
+    shouldBe("contextAttribs.alpha", "" + alpha);
+    if (contextVersion < 2) {
+        if (!stencil)
+            shouldBeFalse("contextAttribs.stencil");
+        else
+            stencil = contextAttribs.stencil;
+        if (!depth)
+            shouldBeFalse("contextAttribs.depth");
+        else
+            depth = contextAttribs.depth;
+        if (!antialias)
+            shouldBeFalse("contextAttribs.antialias");
+        else
+            antialias = contextAttribs.antialias;
+    } else {
+        shouldBe("contextAttribs.stencil", "" + stencil);
+        shouldBe("contextAttribs.depth", "" + depth);
+        shouldBe("contextAttribs.antialias", "" + antialias);
+    }
+
+    if (alpha)
+        shouldBeGreaterThanOrEqual("gl.getParameter(gl.ALPHA_BITS)", "8");
+    else
+        shouldBe("gl.getParameter(gl.ALPHA_BITS)", "0");
+    if (stencil)
+        shouldBeGreaterThanOrEqual("gl.getParameter(gl.STENCIL_BITS)", "8");
+    else
+        shouldBe("gl.getParameter(gl.STENCIL_BITS)", "0");
+    if (depth)
+        shouldBeGreaterThanOrEqual("gl.getParameter(gl.DEPTH_BITS)", "16");
+    else
+        shouldBe("gl.getParameter(gl.DEPTH_BITS)", "0");
+
+    var correctColor = alpha ? [0, 0, 0, 0] : [0, 0, 0, 255];
+    wtu.checkCanvas(gl, correctColor);
+
+    debug("Testing default framebuffer.");
+    checkDraw(alpha, stencil, depth, antialias);
+
+    if (fbHasColor) {
+        debug("Testing bound framebuffer object.");
+        gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+        gl.clearColor(0, 0, 0, 0);
+        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);
+        checkDraw(true, fbHasStencil, fbHasDepth, false);
+        gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+    }
+}
+
+function runTest()
+{
+    testDefault();
+    let cases = [false, true];
+    for (let alpha of cases) {
+        for (let stencil of cases) {
+            for (let depth of cases) {
+                for (let antialias of cases) {
+                    testAttributesAffectContext(alpha, stencil, depth, antialias);
+                }
+            }
+        }
+    }
+    finishTest();
+}
+</script>
+</head>
+<body onload="init()">
+<div id="description"></div>
+<div id="console"></div>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation-and-destruction.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation-and-destruction.html
new file mode 100644
index 0000000000..72324b5f17
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation-and-destruction.html
@@ -0,0 +1,35 @@
+<!--
+Copyright (c) 2019 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>Test that contexts are freed and garbage collected reasonably</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/iterable-test.js"> </script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description();
+
+var wtu = WebGLTestUtils;
+
+var test = IterableTest.createContextCreationAndDestructionTest();
+var iterations = parseInt(wtu.getUrlOptions().iterations, 10) || 50;
+IterableTest.run(test, iterations);
+
+var successfullyParsed = true;
+</script>
+
+</body>
+</html>
+
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation.html
new file mode 100644
index 0000000000..ceeb5b092b
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-creation.html
@@ -0,0 +1,35 @@
+<!--
+Copyright (c) 2019 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>Test that you can create large numbers of WebGL contexts.</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/iterable-test.js"> </script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description();
+
+var wtu = WebGLTestUtils;
+
+var test = IterableTest.createContextCreationTest();
+var iterations = parseInt(wtu.getUrlOptions().iterations, 10) || 50;
+IterableTest.run(test, iterations);
+
+var successfullyParsed = true;
+</script>
+
+</body>
+</html>
+
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-eviction-with-garbage-collection.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-eviction-with-garbage-collection.html
new file mode 100644
index 0000000000..1898e73520
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-eviction-with-garbage-collection.html
@@ -0,0 +1,57 @@
+<!--
+Copyright (c) 2019 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>Test that context eviction and garbage collection do not interfere with each other</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";
+// See http://crbug.com/374086 for original failing case.
+description("Test that context eviction and garbage collection do not interfere with each other.");
+var wtu = WebGLTestUtils;
+
+var total_iteration = 50;
+var array_count = 10;
+
+var bank = [];
+for (var i = 0; i < array_count; i++)
+  bank[i] = [];
+
+for (var iter = 0; iter < total_iteration; ++iter) {
+  for (var i = 0; i < array_count; i++)
+    bank[i][iter * i] = iter;
+
+  var canvas = document.createElement('canvas');
+  var gl = wtu.create3DContext(canvas);
+  canvas.width = 50;
+  canvas.height = 50;
+  var program = wtu.setupTexturedQuad(gl);
+  shouldBeTrue("program != null");
+  var tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  var pixel = new Uint8Array([0, 255, 0, 255]);
+  gl.texImage2D(
+    gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, pixel);
+  wtu.clearAndDrawUnitQuad(gl);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors from iteration " + iter);
+}
+
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+
+</body>
+</html>
+
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-hidden-alpha.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-hidden-alpha.html
new file mode 100644
index 0000000000..ed67fc0093
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-hidden-alpha.html
@@ -0,0 +1,166 @@
+<!--
+Copyright (c) 2019 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>
+<script id='vs' type='x-shader/x-vertex'>
+    attribute vec2 aPosCoord;
+
+    void main(void) {
+        gl_Position = vec4(aPosCoord, 0.0, 1.0);
+    }
+</script>
+
+<script id='fs' type='x-shader/x-fragment'>
+    precision mediump float;
+
+    void main(void) {
+        gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+    }
+</script>
+<script>
+"use strict";
+
+var posCoords_arr = new Float32Array(2 * 4);
+var posCoords_buff = null;
+function DrawQuad(gl, prog, x0, y0, x1, y1) {
+    gl.useProgram(prog);
+
+    if (!posCoords_buff) {
+        posCoords_buff = gl.createBuffer();
+    }
+    gl.bindBuffer(gl.ARRAY_BUFFER, posCoords_buff);
+    posCoords_arr[0] = x0;
+    posCoords_arr[1] = y0;
+
+    posCoords_arr[2] = x1;
+    posCoords_arr[3] = y0;
+
+    posCoords_arr[4] = x0;
+    posCoords_arr[5] = y1;
+
+    posCoords_arr[6] = x1;
+    posCoords_arr[7] = y1;
+    gl.bufferData(gl.ARRAY_BUFFER, posCoords_arr, gl.STREAM_DRAW);
+
+    gl.enableVertexAttribArray(prog.aPosCoord);
+    gl.vertexAttribPointer(prog.aPosCoord, 2, gl.FLOAT, false, 0, 0);
+
+    gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
+}
+
+function DrawSquare(gl, prog, size) {
+    DrawQuad(gl, prog, -size, -size, size, size);
+}
+
+function Reset(gl) {
+    gl.canvas.width += 1;
+    gl.canvas.width -= 1;
+}
+
+var iColor;
+var pixel;
+var dataURL_pre;
+var dataURL_post;
+
+function Test(gl, prog, shouldFinish) {
+    gl.enable(gl.BLEND);
+    gl.blendFunc(gl.ZERO, gl.DST_ALPHA);
+
+    iColor = 64;
+    var fColor = iColor / 255.0;
+
+    //////////////////
+
+    debug('clear(R,G,B,0)');
+
+    Reset(gl);
+
+    gl.clearColor(fColor, fColor, fColor, 0.0);
+    gl.clear(gl.COLOR_BUFFER_BIT);
+
+    dataURL_pre = gl.canvas.toDataURL();
+    //console.log('Before blending: ' + dataURL_pre);
+
+    DrawSquare(gl, prog, 0.7);
+
+    WebGLTestUtils.checkCanvasRect(gl, gl.drawingBufferWidth/2,
+                                   gl.drawingBufferHeight/2, 1, 1,
+                                   [iColor, iColor, iColor, 255],
+                                   'Should blend as if alpha is 1.0.');
+
+    dataURL_post = gl.canvas.toDataURL();
+    //console.log('After blending: ' + dataURL_post);
+    shouldBe("dataURL_post", "dataURL_pre");
+
+    //////////////////
+
+    debug('mask(R,G,B,0), clear(R,G,B,1)');
+
+    Reset(gl);
+
+    gl.colorMask(true, true, true, false);
+    gl.clearColor(fColor, fColor, fColor, 1.0);
+    gl.clear(gl.COLOR_BUFFER_BIT);
+    gl.colorMask(true, true, true, true);
+
+    dataURL_pre = gl.canvas.toDataURL();
+    //console.log('Before blending: ' + dataURL_pre);
+
+    DrawSquare(gl, prog, 0.7);
+
+    WebGLTestUtils.checkCanvasRect(gl, gl.drawingBufferWidth/2,
+                                   gl.drawingBufferHeight/2, 1, 1,
+                                   [iColor, iColor, iColor, 255],
+                                   'Should blend as if alpha is 1.0.');
+
+    dataURL_post = gl.canvas.toDataURL();
+    //console.log('After blending: ' + dataURL_post);
+    shouldBe("dataURL_post", "dataURL_pre");
+
+    ////////////////
+
+    WebGLTestUtils.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors");
+
+    if (shouldFinish)
+        finishTest();
+}
+
+var gl;
+function init() {
+    var canvas = document.getElementById('canvas');
+    var attribs = {
+        alpha: false,
+        antialias: false,
+        premultipliedAlpha: false,
+    };
+    gl = canvas.getContext('experimental-webgl', attribs);
+    shouldBeNonNull(gl);
+    shouldBe("gl.getParameter(gl.ALPHA_BITS)", "0");
+
+    var prog = WebGLTestUtils.setupProgram(gl, ['vs', 'fs']);
+    shouldBeNonNull(prog);
+    prog.aPosCoord = gl.getAttribLocation(prog, 'aPosCoord');
+
+    Test(gl, prog, false);
+
+    requestAnimationFrame(function(){ Test(gl, prog, true); });
+}
+
+</script>
+</head>
+<body onload="init()">
+<canvas id='canvas'></canvas>
+<br/>
+<div id="description"></div>
+<div id="console"></div>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost-restored.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost-restored.html
new file mode 100644
index 0000000000..6942e3d1ce
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost-restored.html
@@ -0,0 +1,287 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<!--
+Copyright (c) 2019 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.
+-->
+<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>
+"use strict";
+var wtu = WebGLTestUtils;
+var canvas;
+var gl;
+var shouldGenerateGLError;
+var WEBGL_lose_context;
+var new_WEBGL_lose_context;
+var bufferObjects;
+var program;
+var texture;
+var texColor = [255, 10, 20, 255];
+var allowRestore;
+var contextLostEventFired;
+var contextRestoredEventFired;
+var OES_vertex_array_object;
+var old_OES_vertex_array_object;
+var vertexArrayObject;
+var OES_texture_float;
+var newExtension;
+
+function init()
+{
+    enableJSTestPreVerboseLogging();
+    description("Tests behavior under a restored context.");
+
+    shouldGenerateGLError = wtu.shouldGenerateGLError;
+    testLosingContext();
+}
+
+function setupTest()
+{
+    canvas = document.createElement("canvas");
+    canvas.width = 1;
+    canvas.height = 1;
+    gl = wtu.create3DContext(canvas);
+    WEBGL_lose_context = getExtensionAndAddProperty(gl, "WEBGL_lose_context");
+    if (!WEBGL_lose_context) {
+        debug("Could not find WEBGL_lose_context extension");
+        return false;
+    }
+
+    // Try to get a few extensions
+    OES_vertex_array_object = getExtensionAndAddProperty(gl, "OES_vertex_array_object");
+    OES_texture_float = getExtensionAndAddProperty(gl, "OES_texture_float");
+
+    return true;
+}
+
+function getExtensionAndAddProperty(gl, name) {
+  var ext = wtu.getExtensionWithKnownPrefixes(gl, name);
+  if (ext) {
+    ext.webglTestProperty = true;
+  }
+  return ext;
+}
+
+function reGetExtensionAndTestForProperty(gl, name, expectProperty) {
+  newExtension = wtu.getExtensionWithKnownPrefixes(gl, name);
+  // NOTE: while getting a extension after context lost/restored is allowed to fail
+  // for the purpose the conformance tests it is not.
+  //
+  // Hypothetically the user can switch GPUs live. For example on Windows, install 2 GPUs,
+  // then in the control panen enable 1, disable the others and visa versa. Since the GPUs
+  // have different capabilities one or the other may not support a particlar extension.
+  //
+  // But, for the purpose of the conformance tests the context is expected to restore
+  // on the same GPU and therefore the extensions that succeeded previously should
+  // succeed on restore.
+  shouldBeTrue("newExtension != null");
+  if (expectProperty) {
+    shouldBeTrue("newExtension.webglTestProperty === true");
+  } else {
+    shouldBeTrue("newExtension.webglTestProperty === undefined");
+  }
+  return newExtension;
+}
+
+function testLosingContext()
+{
+    if (!setupTest()) {
+        finishTest();
+        return;
+    }
+
+    debug("Test losing a context and inability to restore it.");
+
+    canvas.addEventListener("webglcontextlost", function(e) {
+       testLostContext(e);
+       // restore the context after this event has exited.
+       setTimeout(function() {
+         // we didn't call prevent default so we should not be able to restore the context
+         shouldGenerateGLError(gl, gl.INVALID_OPERATION, "WEBGL_lose_context.restoreContext()");
+         testLosingAndRestoringContext();
+       }, 0);
+    });
+    canvas.addEventListener("webglcontextrestored", testShouldNotRestoreContext);
+    allowRestore = false;
+    contextLostEventFired = false;
+    contextRestoredEventFired = false;
+
+    testOriginalContext();
+    WEBGL_lose_context.loseContext();
+    // The context should be lost immediately.
+    shouldBeTrue("gl.isContextLost()");
+    shouldBe("gl.getError()", "gl.CONTEXT_LOST_WEBGL");
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+    // gl methods should be no-ops
+    shouldGenerateGLError(gl, gl.NO_ERROR, "gl.blendFunc(gl.TEXTURE_2D, gl.TEXTURE_CUBE_MAP)");
+    // but the event should not have been fired.
+    shouldBeFalse("contextLostEventFired");
+}
+
+function testLosingAndRestoringContext()
+{
+    if (!setupTest())
+        finishTest();
+
+    debug("");
+    debug("Test losing and restoring a context.");
+
+    canvas.addEventListener("webglcontextlost", function(e) {
+      testLostContext(e);
+      // restore the context after this event has exited.
+      setTimeout(function() {
+        shouldGenerateGLError(gl, gl.NO_ERROR, "WEBGL_lose_context.restoreContext()");
+        // Calling restoreContext() twice should not cause error or crash
+        shouldGenerateGLError(gl, gl.NO_ERROR, "WEBGL_lose_context.restoreContext()");
+        // The context should still be lost. It will not get restored until the
+        // webglrestorecontext event is fired.
+        shouldBeTrue("gl.isContextLost()");
+        shouldBe("gl.getError()", "gl.NO_ERROR");
+        // gl methods should still be no-ops
+        shouldGenerateGLError(gl, gl.NO_ERROR, "gl.blendFunc(gl.TEXTURE_2D, gl.TEXTURE_CUBE_MAP)");
+      }, 0);
+    });
+    canvas.addEventListener("webglcontextrestored", function() {
+      testRestoredContext();
+      finishTest();
+    });
+    allowRestore = true;
+    contextLostEventFired = false;
+    contextRestoredEventFired = false;
+
+    testOriginalContext();
+    WEBGL_lose_context.loseContext();
+    // The context should be lost immediately.
+    shouldBeTrue("gl.isContextLost()");
+    shouldBe("gl.getError()", "gl.CONTEXT_LOST_WEBGL");
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+    // gl methods should be no-ops
+    shouldGenerateGLError(gl, gl.NO_ERROR, "gl.blendFunc(gl.TEXTURE_2D, gl.TEXTURE_CUBE_MAP)");
+    // but the event should not have been fired.
+    shouldBeFalse("contextLostEventFired");
+}
+
+function testRendering()
+{
+    gl.clearColor(0, 0, 0, 255);
+    gl.colorMask(1, 1, 1, 0);
+    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
+
+    program = wtu.setupSimpleTextureProgram(gl);
+    bufferObjects = wtu.setupUnitQuad(gl);
+    texture = wtu.createColoredTexture(gl, canvas.width, canvas.height, texColor);
+
+    gl.uniform1i(gl.getUniformLocation(program, "tex"), 0);
+    wtu.clearAndDrawUnitQuad(gl, [0, 0, 0, 255]);
+
+    var compare = texColor.slice(0, 3);
+    wtu.checkCanvasRect(gl, 0, 0, canvas.width, canvas.height, compare, "shouldBe " + compare);
+
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+}
+
+function testOriginalContext()
+{
+    debug("Test valid context");
+    shouldBeFalse("gl.isContextLost()");
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+    testRendering();
+    debug("");
+}
+
+function testLostContext(e)
+{
+    debug("Test lost context");
+    shouldBeFalse("contextLostEventFired");
+    contextLostEventFired = true;
+    shouldBeTrue("gl.isContextLost()");
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+    debug("");
+    if (allowRestore)
+      e.preventDefault();
+}
+
+function testShouldNotRestoreContext(e)
+{
+    testFailed("Should not restore the context unless preventDefault is called on the context lost event");
+    debug("");
+}
+
+function testResources(expected)
+{
+    var tests = [
+        "gl.bindTexture(gl.TEXTURE_2D, texture)",
+        "gl.useProgram(program)",
+        "gl.bindBuffer(gl.ARRAY_BUFFER, bufferObjects[0])",
+    ];
+
+    for (var i = 0; i < tests.length; ++i)
+        shouldGenerateGLError(gl, expected, tests[i]);
+}
+
+function testOESTextureFloat() {
+  if (OES_texture_float) {
+    // Extension must still be lost.
+    var tex = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, tex);
+    shouldGenerateGLError(gl, gl.INVALID_ENUM, "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.FLOAT, null)");
+    // Try re-enabling extension
+    OES_texture_float = reGetExtensionAndTestForProperty(gl, "OES_texture_float", false);
+    shouldGenerateGLError(gl, gl.NO_ERROR, "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.FLOAT, null)");
+  }
+}
+
+function testOESVertexArrayObject() {
+  if (OES_vertex_array_object) {
+    // Extension must still be lost.
+    shouldBeNull("OES_vertex_array_object.createVertexArrayOES()");
+    // Try re-enabling extension
+
+    old_OES_vertex_array_object = OES_vertex_array_object;
+    OES_vertex_array_object = reGetExtensionAndTestForProperty(gl, "OES_vertex_array_object", false);
+    shouldBeTrue("OES_vertex_array_object.createVertexArrayOES() != null");
+    shouldBeTrue("old_OES_vertex_array_object.createVertexArrayOES() == null");
+  }
+}
+
+function testExtensions() {
+  testOESTextureFloat();
+  testOESVertexArrayObject();
+  // Only the WEBGL_lose_context extension should be the same object after context lost.
+  new_WEBGL_lose_context = reGetExtensionAndTestForProperty(gl, "WEBGL_lose_context", true);
+}
+
+function testRestoredContext()
+{
+    debug("Test restored context");
+    shouldBeFalse("contextRestoredEventFired");
+    contextRestoredEventFired = true;
+    shouldBeFalse("gl.isContextLost()");
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+
+    // Validate that using old resources fails.
+    testResources(gl.INVALID_OPERATION);
+
+    testRendering();
+
+    // Validate new resources created in testRendering().
+    testResources(gl.NO_ERROR);
+
+    testExtensions();
+
+    debug("");
+}
+
+
+</script>
+</head>
+<body onload="init()">
+<div id="description"></div>
+<div id="console"></div>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost.html
new file mode 100644
index 0000000000..31d07a94a9
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-lost.html
@@ -0,0 +1,379 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<!--
+Copyright (c) 2019 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.
+-->
+<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>
+"use strict";
+var wtu;
+var canvas;
+var gl;
+var shouldGenerateGLError;
+var extensionName;
+var extension;
+
+var buffer;
+var framebuffer;
+var program;
+var renderbuffer;
+var shader;
+var texture;
+var uniformLocation;
+var arrayBuffer;
+var arrayBufferView
+var image;
+var video;
+var canvas2d;
+var ctx2d;
+var imageData;
+var float32array;
+var int32array;
+var OES_vertex_array_object;
+var vertexArrayObject;
+
+var secondCanvas;
+var secondGL;
+
+function init()
+{
+    wtu = WebGLTestUtils;
+    canvas = document.getElementById("canvas");
+    gl = wtu.create3DContext(canvas);
+    secondCanvas = document.getElementById("canvas2");
+    secondGL = wtu.create3DContext(secondCanvas);
+    shouldGenerateGLError = wtu.shouldGenerateGLError;
+
+    description("Tests behavior under a lost context");
+
+    // call testValidContext() before checking for the extension, because this is where we check
+    // for the isContextLost() method, which we want to do regardless of the extension's presence.
+    testValidContext();
+
+    extensionName = wtu.getSupportedExtensionWithKnownPrefixes(gl, "WEBGL_lose_context");
+    if (!extensionName) {
+        debug("Could not find WEBGL_lose_context extension");
+        finishTest();
+        return false;
+    }
+    extension = gl.getExtension(extensionName);
+
+    // need an extension that exposes new API methods.
+    OES_vertex_array_object = wtu.getExtensionWithKnownPrefixes(gl, "OES_vertex_array_object");
+
+    canvas.addEventListener("webglcontextlost", testLostContext, false);
+
+    // We need to initialize |uniformLocation| before losing context.
+    // Otherwise gl.getUniform() when context is lost will throw.
+    uniformLocation = gl.getUniformLocation(program, "tex");
+    loseContext();
+}
+
+function loseContext()
+{
+    debug("");
+    debug("Lose context");
+
+    // Note: this will cause the context to be lost, but the
+    // webglcontextlost event listener to be queued.
+    extension.loseContext();
+    debug("");
+}
+
+function testValidContext()
+{
+    debug("Test valid context");
+
+    shouldBeFalse("gl.isContextLost()");
+
+    arrayBuffer = new ArrayBuffer(4);
+    arrayBufferView = new Int8Array(arrayBuffer);
+
+    // Generate resources for testing.
+    buffer = gl.createBuffer();
+    gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
+    framebuffer = gl.createFramebuffer();
+    gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+    program = wtu.setupSimpleTextureProgram(gl);
+    renderbuffer = gl.createRenderbuffer();
+    gl.bindRenderbuffer(gl.RENDERBUFFER, renderbuffer);
+    shader = gl.createShader(gl.VERTEX_SHADER);
+    texture = gl.createTexture();
+    gl.bindTexture(gl.TEXTURE_2D, texture);
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+
+    // Test is queries that will later be false
+    shouldGenerateGLError(gl, gl.NO_ERROR, "gl.enable(gl.BLEND)");
+    shouldBeTrue("gl.isBuffer(buffer)");
+    shouldBeTrue("gl.isEnabled(gl.BLEND)");
+    shouldBeTrue("gl.isFramebuffer(framebuffer)");
+    shouldBeTrue("gl.isProgram(program)");
+    shouldBeTrue("gl.isRenderbuffer(renderbuffer)");
+    shouldBeTrue("gl.isShader(shader)");
+    shouldBeTrue("gl.isTexture(texture)");
+
+    if (OES_vertex_array_object) {
+      vertexArrayObject = OES_vertex_array_object.createVertexArrayOES();
+      shouldBe("gl.getError()", "gl.NO_ERROR");
+      shouldBeTrue("OES_vertex_array_object.isVertexArrayOES(vertexArrayObject)");
+    }
+}
+
+function testGLNOErrorFunctions(tests) {
+  tests.forEach(function(test) {
+      shouldGenerateGLError(gl, gl.NO_ERROR, test);
+  });
+}
+
+function testFunctionsThatReturnNULL(tests) {
+  tests.forEach(function(test) {
+      shouldBeNull(test);
+  });
+}
+
+function testUploadingLostContextToTexture() {
+  debug("Testing uploading a canvas with a lost WebGL context to a texture");
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors at beginning");
+  let texture = secondGL.createTexture();
+  secondGL.bindTexture(secondGL.TEXTURE_2D, texture);
+  secondGL.texImage2D(secondGL.TEXTURE_2D, 0, secondGL.RGBA, secondGL.RGBA, secondGL.UNSIGNED_BYTE, canvas);
+  wtu.glErrorShouldBe(secondGL, [secondGL.INVALID_OPERATION, secondGL.NO_ERROR], "Should not crash when uploading canvas with lost WebGL context to a texture");
+}
+
+function testLostContext()
+{
+    debug("Test lost context");
+
+    // Functions with special return values.
+    shouldBeTrue("gl.isContextLost()");
+    shouldBe("gl.getError()", "gl.CONTEXT_LOST_WEBGL");
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+    shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_UNSUPPORTED");
+    shouldBe("gl.getAttribLocation(program, 'u_modelViewProjMatrix')", "-1");
+    shouldBe("gl.getVertexAttribOffset(0, gl.VERTEX_ATTRIB_ARRAY_POINTER)", "0");
+
+    // Attempt resize of lost context should succeed, still lost.
+    gl.canvas.width = gl.canvas.width; // Try to hit any same-size resize path.
+    shouldBeTrue("gl.isContextLost()");
+
+    const newSize = gl.canvas.width + 1;
+    gl.canvas.width = newSize;
+    shouldBe("gl.canvas.width", newSize);
+    shouldBeTrue("gl.isContextLost()");
+
+    // Test the extension itself.
+    shouldGenerateGLError(gl, gl.INVALID_OPERATION, "extension.loseContext()");
+
+    image = document.createElement("img");
+    video = document.createElement("video");
+    canvas2d = document.createElement("canvas");
+    ctx2d = canvas2d.getContext("2d");
+    imageData = ctx2d.createImageData(1, 1);
+    float32array = new Float32Array(1);
+    int32array = new Int32Array(1);
+
+    // Functions returning void should return immediately.
+    // This is untestable, but we can at least be sure they cause no errors
+    // and the codepaths are exercised.
+    var voidTests = [
+        "gl.activeTexture(gl.TEXTURE0)",
+        "gl.attachShader(program, shader)",
+        "gl.bindBuffer(gl.ARRAY_BUFFER, buffer)",
+        "gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer)",
+        "gl.bindRenderbuffer(gl.RENDERBUFFER, renderbuffer)",
+        "gl.bindTexture(gl.TEXTURE_2D, texture)",
+        "gl.blendColor(1.0, 1.0, 1.0, 1.0)",
+        "gl.blendEquation(gl.FUNC_ADD)",
+        "gl.blendEquationSeparate(gl.FUNC_ADD, gl.FUNC_ADD)",
+        "gl.blendFunc(gl.ONE, gl.ONE)",
+        "gl.blendFuncSeparate(gl.ONE, gl.ONE, gl.ONE, gl.ONE)",
+        "gl.bufferData(gl.ARRAY_BUFFER, 0, gl.STATIC_DRAW)",
+        "gl.bufferData(gl.ARRAY_BUFFER, arrayBufferView, gl.STATIC_DRAW)",
+        "gl.bufferData(gl.ARRAY_BUFFER, arrayBuffer, gl.STATIC_DRAW)",
+        "gl.bufferSubData(gl.ARRAY_BUFFRE, 0, arrayBufferView)",
+        "gl.bufferSubData(gl.ARRAY_BUFFRE, 0, arrayBuffer)",
+        "gl.clear(gl.COLOR_BUFFER_BIT)",
+        "gl.clearColor(1, 1, 1, 1)",
+        "gl.clearDepth(1)",
+        "gl.clearStencil(0)",
+        "gl.colorMask(1, 1, 1, 1)",
+        "gl.compileShader(shader)",
+        "gl.copyTexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 0, 0, 0, 0, 0)",
+        "gl.copyTexSubImage2D(gl.TEXTURE_2D, 0, 0, 0, 0, 0, 0, 0)",
+        "gl.cullFace(gl.FRONT)",
+        "gl.deleteBuffer(buffer)",
+        "gl.deleteFramebuffer(framebuffer)",
+        "gl.deleteProgram(program)",
+        "gl.deleteRenderbuffer(renderbuffer)",
+        "gl.deleteShader(shader)",
+        "gl.deleteTexture(texture)",
+        "gl.depthFunc(gl.NEVER)",
+        "gl.depthMask(0)",
+        "gl.depthRange(0, 1)",
+        "gl.detachShader(program, shader)",
+        "gl.disable(gl.BLEND)",
+        "gl.disableVertexAttribArray(0)",
+        "gl.drawArrays(gl.POINTS, 0, 0)",
+        "gl.drawElements(gl.POINTS, 0, gl.UNSIGNED_SHORT, 0)",
+        "gl.enable(gl.BLEND)",
+        "gl.enableVertexAttribArray(0)",
+        "gl.finish()",
+        "gl.flush()",
+        "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, renderbuffer)",
+        "gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0)",
+        "gl.frontFace(gl.CW)",
+        "gl.generateMipmap(gl.TEXTURE_2D)",
+        "gl.hint(gl.GENERATE_MIPMAP_HINT, gl.FASTEST)",
+        "gl.lineWidth(0)",
+        "gl.linkProgram(program)",
+        "gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 0)",
+        "gl.polygonOffset(0, 0)",
+        "gl.readPixels(0, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, arrayBufferView)",
+        "gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, 0, 0)",
+        "gl.sampleCoverage(0, 0)",
+        "gl.scissor(0, 0, 0, 0)",
+        "gl.shaderSource(shader, '')",
+        "gl.stencilFunc(gl.NEVER, 0, 0)",
+        "gl.stencilFuncSeparate(gl.FRONT, gl.NEVER, 0, 0)",
+        "gl.stencilMask(0)",
+        "gl.stencilMaskSeparate(gl.FRONT, 0)",
+        "gl.stencilOp(gl.KEEP, gl.KEEP, gl.KEEP)",
+        "gl.stencilOpSeparate(gl.FRONT, gl.KEEP, gl.KEEP, gl.KEEP)",
+        "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, arrayBufferView)",
+        "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, imageData)",
+        "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image)",
+        "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, canvas2d)",
+        "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, video)",
+        "gl.texParameterf(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)",
+        "gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)",
+        "gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, arrayBufferView)",
+        "gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, imageData)",
+        "gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, image)",
+        "gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, canvas2d)",
+        "gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, gl.RGBA, gl.UNSIGNED_BYTE, video)",
+        "gl.uniform1f(uniformLocation, 0)",
+        "gl.uniform1fv(uniformLocation, float32array)",
+        "gl.uniform1fv(uniformLocation, [0])",
+        "gl.uniform1i(uniformLocation, 0)",
+        "gl.uniform1iv(uniformLocation, int32array)",
+        "gl.uniform1iv(uniformLocation, [0])",
+        "gl.uniform2f(uniformLocation, 0, 0)",
+        "gl.uniform2fv(uniformLocation, float32array)",
+        "gl.uniform2fv(uniformLocation, [0, 0])",
+        "gl.uniform2i(uniformLocation, 0, 0)",
+        "gl.uniform2iv(uniformLocation, int32array)",
+        "gl.uniform2iv(uniformLocation, [0, 0])",
+        "gl.uniform3f(uniformLocation, 0, 0, 0)",
+        "gl.uniform3fv(uniformLocation, float32array)",
+        "gl.uniform3fv(uniformLocation, [0, 0, 0])",
+        "gl.uniform3i(uniformLocation, 0, 0, 0)",
+        "gl.uniform3iv(uniformLocation, int32array)",
+        "gl.uniform3iv(uniformLocation, [0, 0, 0])",
+        "gl.uniform4f(uniformLocation, 0, 0, 0, 0)",
+        "gl.uniform4fv(uniformLocation, float32array)",
+        "gl.uniform4fv(uniformLocation, [0, 0, 0, 0])",
+        "gl.uniform4i(uniformLocation, 0, 0, 0, 0)",
+        "gl.uniform4iv(uniformLocation, int32array)",
+        "gl.uniform4iv(uniformLocation, [0, 0, 0, 0])",
+        "gl.uniformMatrix2fv(uniformLocation, false, float32array)",
+        "gl.uniformMatrix2fv(uniformLocation, false, [0, 0, 0, 0])",
+        "gl.uniformMatrix3fv(uniformLocation, false, float32array)",
+        "gl.uniformMatrix3fv(uniformLocation, false, [0, 0, 0, 0, 0, 0, 0, 0, 0])",
+        "gl.uniformMatrix4fv(uniformLocation, false, float32array)",
+        "gl.uniformMatrix4fv(uniformLocation, false, [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])",
+        "gl.useProgram(program)",
+        "gl.validateProgram(program)",
+        "gl.vertexAttrib1f(0, 0)",
+        "gl.vertexAttrib1fv(0, float32array)",
+        "gl.vertexAttrib1fv(0, [0])",
+        "gl.vertexAttrib2f(0, 0, 0)",
+        "gl.vertexAttrib2fv(0, float32array)",
+        "gl.vertexAttrib2fv(0, [0, 0])",
+        "gl.vertexAttrib3f(0, 0, 0, 0)",
+        "gl.vertexAttrib3fv(0, float32array)",
+        "gl.vertexAttrib3fv(0, [0, 0, 0])",
+        "gl.vertexAttrib4f(0, 0, 0, 0, 0)",
+        "gl.vertexAttrib4fv(0, float32array)",
+        "gl.vertexAttrib4fv(0, [0, 0, 0, 0])",
+        "gl.vertexAttribPointer(0, 0, gl.FLOAT, false, 0, 0)",
+        "gl.viewport(0, 0, 0, 0)",
+    ];
+    testGLNOErrorFunctions(voidTests);
+
+    // Functions return nullable values should all return null.
+    var nullTests = [
+        "gl.createBuffer()",
+        "gl.createFramebuffer()",
+        "gl.createProgram()",
+        "gl.createRenderbuffer()",
+        "gl.createShader(gl.GL_VERTEX_SHADER)",
+        "gl.createTexture()",
+        "gl.getActiveAttrib(program, 0)",
+        "gl.getActiveUniform(program, 0)",
+        "gl.getAttachedShaders(program)",
+        "gl.getBufferParameter(gl.ARRAY_BUFFER, gl.BUFFER_SIZE)",
+        "gl.getContextAttributes()",
+        "gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)",
+        "gl.getParameter(gl.CURRENT_PROGRAM)",
+        "gl.getProgramInfoLog(program)",
+        "gl.getProgramParameter(program, gl.LINK_STATUS)",
+        "gl.getRenderbufferParameter(gl.RENDERBUFFER, gl.RENDERBUFFER_WIDTH)",
+        "gl.getShaderInfoLog(shader)",
+        "gl.getShaderParameter(shader, gl.SHADER_TYPE)",
+        "gl.getShaderSource(shader)",
+        "gl.getTexParameter(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S)",
+        "gl.getUniform(program, uniformLocation)",
+        "gl.getUniformLocation(program, 'vPosition')",
+        "gl.getVertexAttrib(0, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)",
+        "gl.getSupportedExtensions()",
+        "gl.getExtension('" + extensionName + "')",
+    ];
+    testFunctionsThatReturnNULL(nullTests);
+
+    // "Is" queries should all return false.
+    shouldBeFalse("gl.isBuffer(buffer)");
+    shouldBeFalse("gl.isEnabled(gl.BLEND)");
+    shouldBeFalse("gl.isFramebuffer(framebuffer)");
+    shouldBeFalse("gl.isProgram(program)");
+    shouldBeFalse("gl.isRenderbuffer(renderbuffer)");
+    shouldBeFalse("gl.isShader(shader)");
+    shouldBeFalse("gl.isTexture(texture)");
+
+    shouldBe("gl.getError()", "gl.NO_ERROR");
+
+    // test extensions
+    if (OES_vertex_array_object) {
+      testGLNOErrorFunctions(
+        [
+          "OES_vertex_array_object.bindVertexArrayOES(vertexArrayObject)",
+          "OES_vertex_array_object.isVertexArrayOES(vertexArrayObject)",
+          "OES_vertex_array_object.deleteVertexArrayOES(vertexArrayObject)",
+        ]);
+      testFunctionsThatReturnNULL(
+        [
+          "OES_vertex_array_object.createVertexArrayOES()",
+        ]);
+    }
+
+    testUploadingLostContextToTexture();
+
+    debug("");
+
+    finishTest();
+}
+
+</script>
+</head>
+<body onload="init()">
+<div id="description"></div>
+<div id="console"></div>
+<canvas id="canvas">
+<canvas id="canvas2">
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-no-alpha-fbo-with-alpha.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-no-alpha-fbo-with-alpha.html
new file mode 100644
index 0000000000..81fc80ee5f
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-no-alpha-fbo-with-alpha.html
@@ -0,0 +1,77 @@
+<!--
+Copyright (c) 2019 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>
+
+<script>
+"use strict";
+
+var wtu = WebGLTestUtils;
+
+// This declaration needs to be global for "shouldBe" to see it
+var gl;
+
+function init()
+{
+    description('Verify that a WebGL context with alpha:false still works correctly after handling textures with an alpha channel.');
+
+    runTest();
+}
+
+function getWebGL(contextAttribs)
+{
+    return wtu.create3DContext("c", contextAttribs);
+}
+
+function runTest()
+{
+    var buf = new Uint8Array(1 * 1 * 4);
+    shouldBeNonNull("gl = getWebGL({ alpha: false, antialias: false })");
+
+    // Clear to black. Alpha channel of clearColor() is ignored.
+    gl.clearColor(0.0, 0.0, 0.0, 0.7);
+    gl.clear(gl.COLOR_BUFFER_BIT);
+    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 0, 255],
+                        "Alpha channel of clearColor should be ignored");
+
+    wtu.waitForComposite(function() {
+        // Make a new framebuffer and attach a texture with an alpha channel.
+        var fbo = gl.createFramebuffer();
+        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+        var texture = gl.createTexture();
+        gl.bindTexture(gl.TEXTURE_2D, texture);
+        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
+
+        // Clear texture. Note that alpha channel is not 1.0.
+        gl.clearColor(1.0, 0.0, 0.0, 0.5);
+        gl.clear(gl.COLOR_BUFFER_BIT);
+        wtu.checkCanvasRect(gl, 0, 0, 1, 1, [255, 0, 0, 128],
+                            "Alpha channel of clearColor should be obeyed for FBO with alpha channel",
+                            1);
+
+        // Bind back buffer and check that its alpha channel is still 1.0.
+        gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+        wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 0, 255],
+                            "Alpha channel of back buffer should still be 255");
+        finishTest();
+    });
+}
+
+</script>
+</head>
+<body onload="init()">
+<div id="description"></div>
+<div id="console"></div>
+<canvas width="20" height="20" style="border: 1px solid blue;" id="c"></canvas>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-upon-reload.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-upon-reload.html
new file mode 100644
index 0000000000..fbd3a61741
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-upon-reload.html
@@ -0,0 +1,72 @@
+<!--
+Copyright (c) 2019 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 Context Release 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>
+</head>
+<body>
+<iframe id="host" style="width: 256px; height: 256px; border: 0;"></iframe>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test ensures that WebGL contexts are released properly upon page reload");
+
+var wtu = WebGLTestUtils;
+
+var host = document.getElementById("host");
+var testIterations = 25;
+var currentIteration = 0;
+
+function refreshFrame() {
+  if(currentIteration < testIterations) {
+    currentIteration++;
+    debug("");
+    debug("Test " + currentIteration + " of " + testIterations);
+    host.src = "resources/context-release-upon-reload-child.html";
+  } else {
+    finishTest();
+  }
+}
+
+function testContext() {
+  var gl = host.contentWindow.glContext;
+  assertMsg(gl != null, "context was created properly");
+
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors");
+
+  if(gl.canvas.width != gl.drawingBufferWidth ||
+    gl.canvas.height != gl.drawingBufferHeight) {
+    testFailed("Buffer was the wrong size: " +
+        gl.drawingBufferWidth + "x" + gl.drawingBufferHeight);
+  } else {
+    testPassed("Buffer was the correct size: " +
+        gl.drawingBufferWidth + "x" + gl.drawingBufferHeight);
+    refreshFrame();
+  }
+
+  gl = null;
+}
+
+window.addEventListener("message", function(event) {
+  if(event.data == "Ready") {
+    testContext();
+  }
+});
+
+refreshFrame();
+
+var successfullyParsed = true;
+</script>
+
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-with-workers.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-with-workers.html
new file mode 100644
index 0000000000..23037fd3c1
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-release-with-workers.html
@@ -0,0 +1,72 @@
+<!--
+Copyright (c) 2019 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 Context Release 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>
+</head>
+<body>
+<iframe id="host" style="width: 256px; height: 256px; border: 0;"></iframe>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+description("This test ensures that WebGL contexts are released properly when a worker is used");
+
+var wtu = WebGLTestUtils;
+
+var host = document.getElementById("host");
+var testIterations = 25;
+var currentIteration = 0;
+
+function refreshFrame() {
+  if(currentIteration < testIterations) {
+    currentIteration++;
+    debug("");
+    debug("Test " + currentIteration + " of " + testIterations);
+    host.src = "resources/context-release-child-with-worker.html";
+  } else {
+    finishTest();
+  }
+}
+
+function testContext() {
+  var gl = host.contentWindow.glContext;
+  assertMsg(gl != null, "context was created properly");
+
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors");
+
+  if(gl.canvas.width != gl.drawingBufferWidth ||
+    gl.canvas.height != gl.drawingBufferHeight) {
+    testFailed("Buffer was the wrong size: " +
+        gl.drawingBufferWidth + "x" + gl.drawingBufferHeight);
+  } else {
+    testPassed("Buffer was the correct size: " +
+        gl.drawingBufferWidth + "x" + gl.drawingBufferHeight);
+    refreshFrame();
+  }
+
+  gl = null;
+}
+
+window.addEventListener("message", function(event) {
+  if(event.data == "Ready") {
+    testContext();
+  }
+});
+
+refreshFrame();
+
+var successfullyParsed = true;
+</script>
+
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-size-change.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-size-change.html
new file mode 100644
index 0000000000..638d7a7099
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-size-change.html
@@ -0,0 +1,92 @@
+<!--
+Copyright (c) 2019 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>
+
+<script>
+"use strict";
+
+// These declarations need to be global for "shouldBe" to see them
+var gl;
+var pixel = [0, 0, 0, 1];
+var canvas;
+
+function init()
+{
+    description('Verify that changing the size of an antialiased WebGL context does not cause it to stop working.');
+
+    runTest();
+}
+
+function getWebGL(canvasWidth, canvasHeight, contextAttribs)
+{
+    canvas = document.createElement("canvas");
+    if (!canvas)
+        return null;
+    canvas.width = canvasWidth;
+    canvas.height = canvasHeight;
+
+    gl = WebGLTestUtils.create3DContext(canvas, contextAttribs);
+    if (!gl)
+        return null;
+
+    return gl;
+}
+
+function runTest()
+{
+    shouldBeNonNull("gl = getWebGL(1, 1, { alpha: false, antialias: true })");
+
+    // Clear to black.
+    gl.clearColor(0.0, 0.0, 0.0, 1.0);
+    gl.clear(gl.COLOR_BUFFER_BIT);
+
+    // Check that the pixel's R channel is 0.
+    var buf = new Uint8Array(1 * 1 * 4);
+    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buf);
+    pixel[0] = buf[0];
+    shouldBeTrue("pixel[0] == 0");
+
+    // Change the size of the canvas.
+    canvas.width = 3;
+    canvas.height = 3;
+
+    // Clear to black.
+    gl.clearColor(0.0, 0.0, 0.0, 1.0);
+    gl.clear(gl.COLOR_BUFFER_BIT);
+
+    // Clear the top-left pixel to white.
+    gl.enable(gl.SCISSOR_TEST);
+    gl.scissor(0, 0, 1, 1);
+    gl.clearColor(1.0, 1.0, 1.0, 1.0);
+    gl.clear(gl.COLOR_BUFFER_BIT);
+
+    // Check that the top-left pixel has R channel 255.
+    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buf);
+    pixel[0] = buf[0];
+    shouldBeTrue("pixel[0] == 255");
+
+    // Check that the bottom-right pixel has R channel 0.
+    gl.readPixels(2, 2, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buf);
+    pixel[0] = buf[0];
+    shouldBeTrue("pixel[0] == 0");
+
+    finishTest();
+}
+
+</script>
+</head>
+<body onload="init()">
+<div id="description"></div>
+<div id="console"></div>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/context-type-test.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-type-test.html
new file mode 100644
index 0000000000..1aa315219a
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/context-type-test.html
@@ -0,0 +1,53 @@
+<!--
+Copyright (c) 2019 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 Canvas 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>
+<canvas id="canvas" style="width: 50px; height: 50px;"> </canvas>
+<canvas id="canvas2d" width="40" height="40"> </canvas>
+<script>
+"use strict";
+description("This test ensures WebGL implementations interact correctly with the canvas tag.");
+
+debug("");
+debug("Canvas.getContext");
+
+assertMsg(window.WebGLRenderingContext,
+          "WebGLRenderingContext should be a member of window");
+assertMsg('WebGLRenderingContext' in window,
+          "WebGLRenderingContext should be 'in' window");
+assertMsg(Object.getPrototypeOf(WebGLRenderingContext.prototype) === Object.prototype,
+          "WebGLRenderingContext should only have Object in it's prototype chain");
+
+var wtu = WebGLTestUtils;
+var canvas = document.getElementById("canvas");
+var gl = wtu.create3DContext(canvas);
+if (!gl) {
+  testFailed("context does not exist");
+} else {
+  testPassed("context exists");
+
+  debug("Checking context type");
+  assertMsg(gl instanceof WebGLRenderingContext,
+            "context type should be WebGLRenderingContext");
+}
+debug("");
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/deleted-object-behavior.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/deleted-object-behavior.html
new file mode 100644
index 0000000000..525f399678
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/deleted-object-behavior.html
@@ -0,0 +1,237 @@
+<!--
+Copyright (c) 2019 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>Deleted Object Behavior</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="canvases">
+<canvas id="canvas1">
+</div>
+<div id="console"></div>
+
+<script>
+"use strict";
+description("Verifies behavior of deleted objects");
+
+const wtu = WebGLTestUtils;
+const canvas1 = document.getElementById("canvas1");
+const sz = 64;
+canvas1.width = sz;
+canvas1.height = sz;
+const gl = wtu.create3DContext("canvas1");
+let tex, rb; // for shouldBe
+
+function testBoundFBOTexture() {
+  debug("Verifies that a texture attached to a bound framebuffer and then deleted is automatically detached");
+
+  let fb = gl.createFramebuffer();
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+  tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, sz, sz, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+  gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors during framebuffer setup");
+  // The WebGL 1.0 spec guarantees that this combination of attachments results
+  // in a complete framebuffer.
+  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE",
+           "Framebuffer should be complete after setup");
+  debug("Texture should still be bound to the context");
+  shouldBe("gl.getParameter(gl.TEXTURE_BINDING_2D)", "tex");
+  // Delete the texture.
+  gl.deleteTexture(tex);
+  debug("Texture should have been unbound from the context");
+  shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_2D)");
+  debug("Framebuffer should report that the texture was detached");
+  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)", "gl.NONE");
+  debug("Framebuffer should be incomplete after texture was deleted");
+  shouldNotBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
+  debug("Texture should not report that it's still a texture after deletion");
+  shouldBe("gl.isTexture(tex)", "false");
+  // Framebuffer should not function.
+  gl.clearColor(0.0, 1.0, 0.0, 1.0);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+  wtu.glErrorShouldBe(gl, gl.INVALID_FRAMEBUFFER_OPERATION, "Framebuffer should not work after deleting its only attachment");
+  // Default framebuffer shouldn't have been touched.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  wtu.checkCanvasRect(gl, 0, 0, sz, sz, [0, 0, 0, 0], "default framebuffer should be transparent black");
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors after verifying default framebuffer's contents");
+  // Attempt to bind deleted texture should fail.
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "from binding deleted texture");
+  debug("");
+  gl.deleteFramebuffer(fb);
+}
+
+function testUnboundFBOTexture() {
+  debug("Verifies that a texture attached to an unbound framebuffer and then deleted remains usable until detached");
+
+  let fb = gl.createFramebuffer();
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+  tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, sz, sz, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+  gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors during framebuffer setup");
+  // The WebGL 1.0 spec guarantees that this combination of attachments results
+  // in a complete framebuffer.
+  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE",
+           "Framebuffer should be complete after setup");
+  // Unbind the framebuffer from the context so that deleting the texture
+  // doesn't automatically unbind it from the framebuffer.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  debug("Texture should still be bound to the context");
+  shouldBe("gl.getParameter(gl.TEXTURE_BINDING_2D)", "tex");
+  // Delete the texture.
+  gl.deleteTexture(tex);
+  debug("Texture should have been unbound from the context");
+  shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_2D)");
+  // Framebuffer should still be complete.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+  debug("Framebuffer should still be complete after texture was deleted");
+  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
+  debug("Framebuffer should report that the texture is still attached");
+  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "tex");
+  debug("Texture should not report that it's still a texture after deletion");
+  shouldBe("gl.isTexture(tex)", "false");
+  // Framebuffer should still function.
+  gl.clearColor(0.0, 1.0, 0.0, 1.0);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+  wtu.checkCanvasRect(gl, 0, 0, sz, sz, [0, 255, 0, 255], "framebuffer should be green");
+  // Deleting texture a second time should not unbind it from the framebuffer.
+  gl.deleteTexture(tex);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "deleting an object twice is not an error");
+  debug("Framebuffer should still report that the texture is attached");
+  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "tex");
+  // Default framebuffer shouldn't have been touched.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  wtu.checkCanvasRect(gl, 0, 0, sz, sz, [0, 0, 0, 0], "default framebuffer should be transparent black");
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors after verifying framebuffers' contents");
+  // Attempt to bind deleted texture should fail.
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "from binding deleted texture");
+  debug("");
+  gl.deleteFramebuffer(fb);
+}
+
+function testBoundFBORenderbuffer() {
+  debug("Verifies that a renderbuffer attached to a bound framebuffer and then deleted is automatically detached");
+
+  let fb = gl.createFramebuffer();
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+  rb = gl.createRenderbuffer();
+  gl.bindRenderbuffer(gl.RENDERBUFFER, rb);
+  gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, sz, sz)
+  gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rb);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors during framebuffer setup");
+  // The WebGL 1.0 spec doesn't guarantee that this framebuffer configuration
+  // will be complete.
+  if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE) {
+    debug("Framebuffer with GL_RGBA4 renderbuffer was incomplete; skipping test");
+    return;
+  }
+  debug("Renderbuffer should still be bound to the context");
+  shouldBe("gl.getParameter(gl.RENDERBUFFER_BINDING)", "rb");
+  // Delete the renderbuffer.
+  gl.deleteRenderbuffer(rb);
+  debug("Renderbuffer should have been unbound from the context");
+  shouldBeNull("gl.getParameter(gl.RENDERBUFFER_BINDING)");
+  debug("Framebuffer should report that the texture was detached");
+  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)", "gl.NONE");
+  debug("Framebuffer should be incomplete after renderbuffer was deleted");
+  shouldNotBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
+  debug("Renderbuffer should not report that it's still a renderbuffer after deletion");
+  shouldBe("gl.isRenderbuffer(rb)", "false");
+  // Framebuffer should not function.
+  gl.clearColor(0.0, 1.0, 0.0, 1.0);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+  wtu.glErrorShouldBe(gl, gl.INVALID_FRAMEBUFFER_OPERATION, "Framebuffer should not work after deleting its only attachment");
+  // Default framebuffer shouldn't have been touched.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  wtu.checkCanvasRect(gl, 0, 0, sz, sz, [0, 0, 0, 0], "default framebuffer should be transparent black");
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors after verifying framebuffers' contents");
+  // Attempt to bind deleted renderbuffer should fail.
+  gl.bindRenderbuffer(gl.RENDERBUFFER, rb);
+  wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "from binding deleted renderbuffer");
+  debug("");
+  gl.deleteFramebuffer(fb);
+}
+
+function testUnboundFBORenderbuffer() {
+  debug("Verifies that a renderbuffer attached to an unbound framebuffer and then deleted remains usable until detached");
+
+  let fb = gl.createFramebuffer();
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+  rb = gl.createRenderbuffer();
+  gl.bindRenderbuffer(gl.RENDERBUFFER, rb);
+  gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, sz, sz)
+  gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rb);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors during framebuffer setup");
+  // The WebGL 1.0 spec doesn't guarantee that this framebuffer configuration
+  // will be complete.
+  if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE) {
+    debug("Framebuffer with GL_RGBA4 renderbuffer was incomplete; skipping test");
+    return;
+  }
+  // Unbind the framebuffer from the context so that deleting the renderbuffer
+  // doesn't automatically unbind it from the framebuffer.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  debug("Renderbuffer should still be bound to the context");
+  shouldBe("gl.getParameter(gl.RENDERBUFFER_BINDING)", "rb");
+  // Delete the renderbuffer.
+  gl.deleteRenderbuffer(rb);
+  debug("Renderbuffer should have been unbound from the context");
+  shouldBeNull("gl.getParameter(gl.RENDERBUFFER_BINDING)");
+  // Framebuffer should still be complete.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
+  debug("Framebuffer should still be complete after renderbuffer was deleted");
+  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
+  debug("Framebuffer should report that the renderbuffer is still attached");
+  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "rb");
+  debug("Renderbuffer should not report that it's still a renderbuffer after deletion");
+  shouldBe("gl.isRenderbuffer(rb)", "false");
+  // Framebuffer should still function.
+  gl.clearColor(0.0, 1.0, 0.0, 1.0);
+  gl.clear(gl.COLOR_BUFFER_BIT);
+  // Use a high tolerance to accommodate low bit depth precision.
+  wtu.checkCanvasRect(gl, 0, 0, sz, sz, [0, 255, 0, 255], "framebuffer should be green", 20);
+  // Deleting renderbuffer a second time should not unbind it from the framebuffer.
+  gl.deleteRenderbuffer(rb);
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "deleting an object twice is not an error");
+  debug("Framebuffer should still report that the renderbuffer is attached");
+  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "rb");
+  // Default framebuffer shouldn't have been touched.
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  wtu.checkCanvasRect(gl, 0, 0, sz, sz, [0, 0, 0, 0], "default framebuffer should be transparent black");
+  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "should be no errors after verifying framebuffers' contents");
+  // Attempt to bind deleted renderbuffer should fail.
+  gl.bindRenderbuffer(gl.RENDERBUFFER, rb);
+  wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "from binding deleted renderbuffer");
+  debug("");
+  gl.deleteFramebuffer(fb);
+}
+
+function runTests() {
+  testBoundFBOTexture();
+  testUnboundFBOTexture();
+  testBoundFBORenderbuffer();
+  testUnboundFBORenderbuffer();
+  finishTest();
+}
+
+requestAnimationFrame(runTests);
+
+var successfullyParsed = true;
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/incorrect-context-object-behaviour.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/incorrect-context-object-behaviour.html
new file mode 100644
index 0000000000..30d9b04708
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/incorrect-context-object-behaviour.html
@@ -0,0 +1,165 @@
+<!--
+Copyright (c) 2019 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>
+<div id="description"></div>
+<div id="console"></div>
+
+<script>
+"use strict";
+description("Tests calling WebGL APIs with objects from other contexts");
+
+var wtu = WebGLTestUtils;
+var contextA = wtu.create3DContext();
+var contextB = wtu.create3DContext();
+var bufferA = contextA.createBuffer();
+var bufferB = contextB.createBuffer();
+var frameBufferA = contextA.createFramebuffer();
+var frameBufferB = contextB.createFramebuffer();
+var programA = wtu.loadStandardProgram(contextA);
+var programB = wtu.loadStandardProgram(contextB);
+var renderBufferA = contextA.createRenderbuffer();
+var renderBufferB = contextB.createRenderbuffer();
+var shaderA = wtu.loadStandardVertexShader(contextA);
+var shaderB = wtu.loadStandardVertexShader(contextB);
+var textureA = contextA.createTexture();
+var textureB = contextB.createTexture();
+var locationA = contextA.getUniformLocation(programA, 'u_modelViewProjMatrix');
+var locationB = contextB.getUniformLocation(programB, 'u_modelViewProjMatrix');
+var uniformData = [];
+
+function generateFloat32Array(length) {
+    uniformData = new Float32Array(length);
+}
+
+function generateFloatArray(length) {
+    uniformData = new Array(length);
+    for (var i = 0; i < length; i++) {
+        uniformData[i] = 0.0;
+    }
+}
+
+function generateInt32Array(length) {
+    uniformData = new Int32Array(length);
+}
+
+function generateIntArray(length) {
+    uniformData = new Array(length);
+    for (var i = 0; i < length; i++) {
+        uniformData[i] = 0;
+    }
+}
+
+// Make the bindable objects valid in both contexts first.
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindBuffer(contextA.ARRAY_BUFFER, bufferA)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindBuffer(contextA.ARRAY_BUFFER, null)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindBuffer(contextB.ARRAY_BUFFER, bufferB)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindBuffer(contextB.ARRAY_BUFFER, null)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindFramebuffer(contextA.FRAMEBUFFER, frameBufferA)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindFramebuffer(contextA.FRAMEBUFFER, null)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindFramebuffer(contextB.FRAMEBUFFER, frameBufferB)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindFramebuffer(contextB.FRAMEBUFFER, null)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindRenderbuffer(contextA.RENDERBUFFER, renderBufferA)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindRenderbuffer(contextA.RENDERBUFFER, null)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindRenderbuffer(contextB.RENDERBUFFER, renderBufferB)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindRenderbuffer(contextB.RENDERBUFFER, null)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindTexture(contextA.TEXTURE_2D, textureA)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.bindTexture(contextA.TEXTURE_2D, null)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindTexture(contextB.TEXTURE_2D, textureB)");
+wtu.shouldGenerateGLError(contextB, contextB.NO_ERROR, "contextB.bindTexture(contextB.TEXTURE_2D, null)");
+
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.attachShader(programA, shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.attachShader(programB, shaderA)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.attachShader(programB, shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.bindAttribLocation(programB, 0, 'foo')");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.bindBuffer(contextA.ARRAY_BUFFER, bufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.bindFramebuffer(contextA.FRAMEBUFFER, frameBufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.bindRenderbuffer(contextA.RENDERBUFFER, renderBufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.bindTexture(contextA.TEXTURE_2D, textureB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.compileShader(shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.deleteBuffer(bufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.deleteFramebuffer(frameBufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.deleteProgram(programB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.deleteRenderbuffer(renderBufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.deleteShader(shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.deleteShader(shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.deleteTexture(textureB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.detachShader(programA, shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.detachShader(programB, shaderA)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.detachShader(programB, shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.framebufferRenderbuffer(contextA.FRAMEBUFFER, contextA.DEPTH_ATTACHMENT, contextA.RENDERBUFFER, renderBufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.framebufferTexture2D(contextA.FRAMEBUFFER, contextA.COLOR_ATTACHMENT0, contextA.TEXTURE_2D, textureB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getActiveAttrib(programB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getActiveUniform(programB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getAttachedShaders(programB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getAttribLocation(programB, 'a_vertex')");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getProgramParameter(programB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getProgramInfoLog(programB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getShaderParameter(shaderB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getShaderInfoLog(shaderB, 0)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getShaderSource(shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getUniform(programB, locationA)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getUniform(programA, locationB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.getUniformLocation(programB, 'u_modelViewProjMatrix')");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.isBuffer(bufferB)");
+shouldBeFalse("contextA.isBuffer(bufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.isFramebuffer(frameBufferB)");
+shouldBeFalse("contextA.isFramebuffer(frameBufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.isProgram(programB)");
+shouldBeFalse("contextA.isProgram(programB)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.isRenderbuffer(renderBufferB)");
+shouldBeFalse("contextA.isRenderbuffer(renderBufferB)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.isShader(shaderB)");
+shouldBeFalse("contextA.isShader(shaderB)");
+wtu.shouldGenerateGLError(contextA, contextA.NO_ERROR, "contextA.isTexture(textureB)");
+shouldBeFalse("contextA.isTexture(textureB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.linkProgram(programB)");
+wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.shaderSource(shaderB, 'foo')");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform1f(locationB, 0.0)");
+generateFloat32Array(1);  wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform1fv(locationB, uniformData)");
+generateFloatArray(1);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform1fv(locationB, uniformData)");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform1i(locationB, 0)");
+generateInt32Array(1);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform1iv(locationB, uniformData)");
+generateIntArray(1);      wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform1iv(locationB, uniformData)");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform2f(locationB, 0.0, 0.0)");
+generateFloat32Array(2);  wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform2fv(locationB, uniformData)");
+generateFloatArray(2);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform2fv(locationB, uniformData)");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform2i(locationB, 0, 0)");
+generateInt32Array(2);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform2iv(locationB, uniformData)");
+generateIntArray(2);      wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform2iv(locationB, uniformData)");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform3f(locationB, 0.0, 0.0, 0.0)");
+generateFloat32Array(3);  wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform3fv(locationB, uniformData)");
+generateFloatArray(3);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform3fv(locationB, uniformData)");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform3i(locationB, 0, 0, 0)");
+generateInt32Array(3);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform3iv(locationB, uniformData)");
+generateIntArray(3);      wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform3iv(locationB, uniformData)");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform4f(locationB, 0.0, 0.0, 0.0, 0.0)");
+generateFloat32Array(4);  wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform4fv(locationB, uniformData)");
+generateFloatArray(4);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform4fv(locationB, uniformData)");
+                          wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform4i(locationB, 0, 0, 0, 0)");
+generateInt32Array(4);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform4iv(locationB, uniformData)");
+generateIntArray(4);      wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniform4iv(locationB, uniformData)");
+generateFloat32Array(4);  wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniformMatrix2fv(locationB, false, uniformData)");
+generateFloatArray(4);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniformMatrix2fv(locationB, false, uniformData)");
+generateFloat32Array(9);  wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniformMatrix3fv(locationB, false, uniformData)");
+generateFloatArray(9);    wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniformMatrix3fv(locationB, false, uniformData)");
+generateFloat32Array(16); wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniformMatrix4fv(locationB, false, uniformData)");
+generateFloatArray(16);   wtu.shouldGenerateGLError(contextA, contextA.INVALID_OPERATION, "contextA.uniformMatrix4fv(locationB, false, uniformData)");
+
+var successfullyParsed = true;
+</script>
+
+<script src="../../js/js-test-post.js"></script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/methods.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/methods.html
new file mode 100644
index 0000000000..d1e47f32a3
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/methods.html
@@ -0,0 +1,178 @@
+<!--
+Copyright (c) 2019 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 Methods 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/tests/context-methods.js"></script>
+</head>
+<body>
+<div id="description"></div>
+<div id="console"></div>
+<canvas id="canvas" style="width: 50px; height: 50px;"> </canvas>
+<script>
+"use strict";
+description("This test ensures that the WebGL context has all the methods in the specification.");
+
+const methods = [
+  "getContextAttributes",
+  "activeTexture",
+  "attachShader",
+  "bindAttribLocation",
+  "bindBuffer",
+  "bindFramebuffer",
+  "bindRenderbuffer",
+  "bindTexture",
+  "blendColor",
+  "blendEquation",
+  "blendEquationSeparate",
+  "blendFunc",
+  "blendFuncSeparate",
+  "bufferData",
+  "bufferSubData",
+  "checkFramebufferStatus",
+  "clear",
+  "clearColor",
+  "clearDepth",
+  "clearStencil",
+  "colorMask",
+  "compileShader",
+  "compressedTexImage2D",
+  "compressedTexSubImage2D",
+  "copyTexImage2D",
+  "copyTexSubImage2D",
+  "createBuffer",
+  "createFramebuffer",
+  "createProgram",
+  "createRenderbuffer",
+  "createShader",
+  "createTexture",
+  "cullFace",
+  "deleteBuffer",
+  "deleteFramebuffer",
+  "deleteProgram",
+  "deleteRenderbuffer",
+  "deleteShader",
+  "deleteTexture",
+  "depthFunc",
+  "depthMask",
+  "depthRange",
+  "detachShader",
+  "disable",
+  "disableVertexAttribArray",
+  "drawArrays",
+  "drawElements",
+  "enable",
+  "enableVertexAttribArray",
+  "finish",
+  "flush",
+  "framebufferRenderbuffer",
+  "framebufferTexture2D",
+  "frontFace",
+  "generateMipmap",
+  "getActiveAttrib",
+  "getActiveUniform",
+  "getAttachedShaders",
+  "getAttribLocation",
+  "getParameter",
+  "getBufferParameter",
+  "getError",
+  "getExtension",
+  "getFramebufferAttachmentParameter",
+  "getProgramParameter",
+  "getProgramInfoLog",
+  "getRenderbufferParameter",
+  "getShaderParameter",
+  "getShaderInfoLog",
+  "getShaderPrecisionFormat",
+  "getShaderSource",
+  "getSupportedExtensions",
+  "getTexParameter",
+  "getUniform",
+  "getUniformLocation",
+  "getVertexAttrib",
+  "getVertexAttribOffset",
+  "hint",
+  "isBuffer",
+  "isContextLost",
+  "isEnabled",
+  "isFramebuffer",
+  "isProgram",
+  "isRenderbuffer",
+  "isShader",
+  "isTexture",
+  "lineWidth",
+  "linkProgram",
+  "pixelStorei",
+  "polygonOffset",
+  "readPixels",
+  "renderbufferStorage",
+  "sampleCoverage",
+  "scissor",
+  "shaderSource",
+  "stencilFunc",
+  "stencilFuncSeparate",
+  "stencilMask",
+  "stencilMaskSeparate",
+  "stencilOp",
+  "stencilOpSeparate",
+  "texImage2D",
+  "texParameterf",
+  "texParameteri",
+  "texSubImage2D",
+  "uniform1f",
+  "uniform1fv",
+  "uniform1i",
+  "uniform1iv",
+  "uniform2f",
+  "uniform2fv",
+  "uniform2i",
+  "uniform2iv",
+  "uniform3f",
+  "uniform3fv",
+  "uniform3i",
+  "uniform3iv",
+  "uniform4f",
+  "uniform4fv",
+  "uniform4i",
+  "uniform4iv",
+  "uniformMatrix2fv",
+  "uniformMatrix3fv",
+  "uniformMatrix4fv",
+  "useProgram",
+  "validateProgram",
+  "vertexAttrib1f",
+  "vertexAttrib1fv",
+  "vertexAttrib2f",
+  "vertexAttrib2fv",
+  "vertexAttrib3f",
+  "vertexAttrib3fv",
+  "vertexAttrib4f",
+  "vertexAttrib4fv",
+  "vertexAttribPointer",
+  "viewport"
+];
+
+debug("");
+debug("Canvas.getContext");
+
+const wtu = WebGLTestUtils;
+const canvas = document.getElementById("canvas");
+const gl = wtu.create3DContext(canvas);
+
+testContextMethods(gl, methods);
+
+debug("");
+var successfullyParsed = true;
+</script>
+<script src="../../js/js-test-post.js"></script>
+
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/premultiplyalpha-test.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/premultiplyalpha-test.html
new file mode 100644
index 0000000000..ecbe251611
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/premultiplyalpha-test.html
@@ -0,0 +1,251 @@
+<!--
+Copyright (c) 2019 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>Test the WebGL premultipliedAlpha context creation flag.</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";
+var wtu = WebGLTestUtils;
+
+// wtu.create3DContext(...) will set antialias to false by default
+// if the antialias property is not set to true explicitly.
+// To cover the antialias case, it needs to set antialias to true
+// explicitly.
+var tests = [
+  // If premultipliedAlpha is true and antialias is false then
+  // [texture]           [canvas]             [dataURL]
+  // 32, 64, 128, 128 -> 64, 128, 255, 128 -> 64, 128, 255, 128
+  { creationAttributes: {},
+    sentColor: [32, 64, 128, 128],
+    expectedColor: [64, 128, 255, 128],
+    errorRange: 2,
+    imageFormat: "image/png"
+  },
+  // If premultipliedAlpha is true and antialias is true then
+  // [texture]           [canvas]             [dataURL]
+  // 32, 64, 128, 128 -> 64, 128, 255, 128 -> 64, 128, 255, 128
+  { creationAttributes: {antialias: true},
+    sentColor: [32, 64, 128, 128],
+    expectedColor: [64, 128, 255, 128],
+    errorRange: 2,
+    imageFormat: "image/png"
+  },
+  // If premultipliedAlpha is true and antialias is false then
+  // [texture]           [canvas]             [texture]
+  // 32, 64, 128, 128 -> 64, 128, 255, 128 -> 64, 128, 255, 128
+  { creationAttributes: {},
+    sentColor: [32, 64, 128, 128],
+    expectedColor: [64, 128, 255, 128],
+    errorRange: 2,
+  },
+  // If premultipliedAlpha is true and antialias is true then
+  // [texture]           [canvas]             [texture]
+  // 32, 64, 128, 128 -> 64, 128, 255, 128 -> 64, 128, 255, 128
+  { creationAttributes: {antialias: true},
+    sentColor: [32, 64, 128, 128],
+    expectedColor: [64, 128, 255, 128],
+    errorRange: 2,
+  },
+  // If premultipliedAlpha is false and antialias is false then
+  // [texture]           [canvas]            [dataURL]
+  // 255, 192, 128, 1 -> 255, 192, 128, 1 -> 255, 192, 128, 1
+  { creationAttributes: {premultipliedAlpha: false},
+    sentColor: [255, 192, 128, 1],
+    expectedColor: [255, 192, 128, 1],
+    errorRange: 0,
+    imageFormat: "image/png"
+  },
+  // If premultipliedAlpha is false and antialias is true then
+  // [texture]           [canvas]            [dataURL]
+  // 255, 192, 128, 1 -> 255, 192, 128, 1 -> 255, 192, 128, 1
+  { creationAttributes: {premultipliedAlpha: false, antialias: true},
+    sentColor: [255, 192, 128, 1],
+    expectedColor: [255, 192, 128, 1],
+    errorRange: 0,
+    imageFormat: "image/png"
+  },
+  // If premultipliedAlpha is false and antialias is false then
+  // [texture]           [canvas]            [texture]
+  // 255, 192, 128, 1 -> 255, 192, 128, 1 -> 255, 192, 128, 1
+  { creationAttributes: {premultipliedAlpha: false},
+    sentColor: [255, 192, 128, 1],
+    expectedColor: [255, 192, 128, 1],
+    errorRange: 0,
+  },
+  // If premultipliedAlpha is false and antialias is true then
+  // [texture]           [canvas]            [texture]
+  // 255, 192, 128, 1 -> 255, 192, 128, 1 -> 255, 192, 128, 1
+  { creationAttributes: {premultipliedAlpha: false, antialias: true},
+    sentColor: [255, 192, 128, 1],
+    expectedColor: [255, 192, 128, 1],
+    errorRange: 0,
+  },
+  // If premultipliedAlpha is false and antialias is false then
+  // [texture]             [canvas]            [dataURL]
+  // 255, 255, 255, 128 -> 255, 255, 255, 128 -> 128, 128, 128, 255
+  { creationAttributes: {premultipliedAlpha: false},
+    sentColor: [255, 255, 255, 128],
+    expectedColor: [128, 128, 128, 255],
+    errorRange: 2,
+    imageFormat: "image/jpeg"
+  },
+  // If premultipliedAlpha is false and antialias is true then
+  // [texture]             [canvas]            [dataURL]
+  // 255, 255, 255, 128 -> 255, 255, 255, 128 -> 128, 128, 128, 255
+  { creationAttributes: {premultipliedAlpha: false, antialias: true},
+    sentColor: [255, 255, 255, 128],
+    expectedColor: [128, 128, 128, 255],
+    errorRange: 2,
+    imageFormat: "image/jpeg"
+  },
+  // If premultipliedAlpha is true and antialias is false then
+  // [texture]             [canvas]            [dataURL]
+  // 128, 128, 128, 128 -> 255, 255, 255, 128 -> 128, 128, 128, 255
+  { creationAttributes: {},
+    sentColor: [128, 128, 128, 128],
+    expectedColor: [128, 128, 128, 255],
+    errorRange: 2,
+    imageFormat: "image/jpeg"
+  },
+  // If premultipliedAlpha is true and antialias is true then
+  // [texture]             [canvas]            [dataURL]
+  // 128, 128, 128, 128 -> 255, 255, 255, 128 -> 128, 128, 128, 255
+  { creationAttributes: {antialias: true},
+    sentColor: [128, 128, 128, 128],
+    expectedColor: [128, 128, 128, 255],
+    errorRange: 2,
+    imageFormat: "image/jpeg"
+  }
+];
+
+var g_count = 0;
+var gl;
+var canvas;
+var premultipliedAlpha;
+
+enableJSTestPreVerboseLogging();
+description("Test the WebGL premultipliedAlpha context creation flag.");
+doNextTest();
+function doNextTest() {
+  if (g_count < tests.length) {
+    var test = tests[g_count++];
+    canvas = document.createElement("canvas");
+    // Need to preserve drawing buffer to load it in a callback
+    test.creationAttributes.preserveDrawingBuffer = true;
+    gl = wtu.create3DContext(canvas, test.creationAttributes);
+    var premultipliedAlpha = test.creationAttributes.premultipliedAlpha != false;
+    var antialias = test.creationAttributes.antialias == true;
+    debug("")
+    debug("testing: premultipliedAlpha: " + premultipliedAlpha
+        + ", antialias: " + antialias
+        + ", imageFormat: " + test.imageFormat);
+
+    if (!gl) {
+      testFailed("context does not exist");
+      doNextTest();
+      return;
+    }
+
+    shouldBe('gl.getContextAttributes().premultipliedAlpha', premultipliedAlpha.toString());
+    shouldBeTrue('gl.getContextAttributes().preserveDrawingBuffer');
+
+    wtu.log(gl.getContextAttributes());
+    var program = wtu.setupTexturedQuad(gl);
+
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors from setup.");
+    var tex = gl.createTexture();
+    wtu.fillTexture(gl, tex, 2, 2, test.sentColor, 0);
+    var loc = gl.getUniformLocation(program, "tex");
+    gl.uniform1i(loc, 0);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+
+    wtu.clearAndDrawUnitQuad(gl);
+    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors from drawing.");
+
+    var loadTexture = function() {
+      debug("loadTexture called");
+      var pngTex = gl.createTexture();
+      // not needed as it's the default
+      // gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, false);
+      wtu.failIfGLError(gl, 'gl.pixelStorei(gl.UNPACK_COLORSPACE_CONVERSION_WEBGL, gl.NONE);');
+      gl.bindTexture(gl.TEXTURE_2D, pngTex);
+      if (test.imageFormat) {
+         // create texture from image
+         gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, this);
+      } else {
+         // create texture from canvas
+         gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, canvas);
+      }
+      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
+      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+      wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors from creating copy.");
+      wtu.clearAndDrawUnitQuad(gl);
+      wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Should be no errors from 2nd drawing.");
+      wtu.checkCanvas(
+         gl, test.expectedColor,
+         "should draw with " + test.expectedColor, test.errorRange);
+
+      doNextTest();
+    }
+
+    var loadTextureError = function() {
+      testFailed("Creating image from canvas failed. Image src: " + this.src);
+      finishTest();
+    }
+
+    var shrinkString = function(string) {
+      if (string.length < 63) {
+        return string;
+      }
+      return string.substr(0, 30) + "..." + string.substr(string.length - 30);
+    }
+
+    if (test.imageFormat) {
+      // Load canvas into string using toDataURL
+      debug("Calling canvas.toDataURL('" + test.imageFormat + "')");
+      var imageUrl = canvas.toDataURL(test.imageFormat);
+      debug("imageUrl = '" + shrinkString(imageUrl) + "'");
+      if (test.imageFormat != "image/png" &&
+          (imageUrl.indexOf("data:image/png,") == 0 ||
+           imageUrl.indexOf("data:image/png;") == 0)) {
+        debug("Image format " + test.imageFormat + " not supported; skipping");
+        setTimeout(doNextTest, 0);
+      } else {
+        // Load string into the texture
+        debug("Waiting for image.onload");
+        var input = wtu.makeImage(imageUrl, loadTexture, loadTextureError);
+      }
+    } else {
+      // Load canvas into the texture asynchronously (to prevent unbounded stack consumption)
+      debug("Waiting for setTimeout");
+      setTimeout(loadTexture, 0);
+    }
+  } else {
+    var successfullyParsed = true;
+    finishTest();
+  }
+}
+
+</script>
+
+</body>
+</html>
+
+
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-child-with-worker.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-child-with-worker.html
new file mode 100644
index 0000000000..66408c0ef2
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-child-with-worker.html
@@ -0,0 +1,55 @@
+<!--
+Copyright (c) 2019 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 style="margin: 0; padding: 0;">
+<head>
+<meta charset="utf-8">
+<title>Simple WebGL context with Worker</title>
+<script src="../../../js/webgl-test-utils.js"> </script>
+</head>
+<body style="margin: 0; padding: 0; overflow: hidden;">
+<canvas id="c" width="1680" height="1050" style="width: 256px; height: 256px;"> <!-- scaled to fit page better -->
+<script id="vshader" type="x-shader/x-vertex">
+attribute vec4 vPosition;
+void main()
+{
+    gl_Position = vPosition;
+}
+</script>
+
+<script id="fshader" type="x-shader/x-fragment">
+void main()
+{
+    gl_FragColor = vec4(1.0,0.0,0.0,1.0);
+}
+</script>
+
+<script>
+"use strict";
+var wtu = WebGLTestUtils;
+var myWorker = new Worker("context-release-worker.js");
+
+var gl = wtu.create3DContext("c", { antialias: false });
+var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["vPosition"]);
+
+var vertexObject = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, vertexObject);
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([ 0,0.75,0, -0.75,-0.75,0, 0.75,-0.75,0 ]), gl.STATIC_DRAW);
+gl.enableVertexAttribArray(0);
+gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);
+
+gl.clearColor(0.0, 0.0, 0.0, 1.0);
+gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
+gl.drawArrays(gl.TRIANGLES, 0, 3);
+
+if (parent) {
+  window.glContext = gl;
+  parent.postMessage("Ready", "*");
+}
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-upon-reload-child.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-upon-reload-child.html
new file mode 100644
index 0000000000..9f06c41d4e
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-upon-reload-child.html
@@ -0,0 +1,54 @@
+<!--
+Copyright (c) 2019 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 style="margin: 0; padding: 0;">
+<head>
+<meta charset="utf-8">
+<title>Simple WebGL context</title>
+<script src="../../../js/webgl-test-utils.js"> </script>
+</head>
+<body style="margin: 0; padding: 0; overflow: hidden;">
+<canvas id="c" width="1680" height="1050" style="width: 256px; height: 256px;"> <!-- scaled to fit page better -->
+<script id="vshader" type="x-shader/x-vertex">
+attribute vec4 vPosition;
+void main()
+{
+    gl_Position = vPosition;
+}
+</script>
+
+<script id="fshader" type="x-shader/x-fragment">
+void main()
+{
+    gl_FragColor = vec4(1.0,0.0,0.0,1.0);
+}
+</script>
+
+<script>
+"use strict";
+var wtu = WebGLTestUtils;
+
+var gl = wtu.create3DContext("c", { antialias: false });
+var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["vPosition"]);
+
+var vertexObject = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, vertexObject);
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([ 0,0.75,0, -0.75,-0.75,0, 0.75,-0.75,0 ]), gl.STATIC_DRAW);
+gl.enableVertexAttribArray(0);
+gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);
+
+gl.clearColor(0.0, 0.0, 0.0, 1.0);
+gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
+gl.drawArrays(gl.TRIANGLES, 0, 3);
+
+if (parent) {
+    window.glContext = gl;
+    parent.postMessage("Ready", "*");
+}
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-worker.js b/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-worker.js
new file mode 100644
index 0000000000..3680117c25
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/resources/context-release-worker.js
@@ -0,0 +1,4 @@
+// Simple worker used to provoke WebGL context release bugs on Chrome
+
+postMessage("Hello World");
+close();
\ No newline at end of file
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/user-defined-properties-on-context.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/user-defined-properties-on-context.html
new file mode 100644
index 0000000000..4029087c1f
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/user-defined-properties-on-context.html
@@ -0,0 +1,49 @@
+<!--
+Copyright (c) 2019 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 User-Defined Properties 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>
+</head>
+<body onload="initialize()">
+<div id="description"></div>
+<div id="console"></div>
+<canvas id="canvas" style="width: 50px; height: 50px;"> </canvas>
+<script>
+"use strict";
+description("This test ensures that if user-defined properties are set on the WebGL context object, that they don't disappear after garbage collection.");
+
+var gl2 = null;
+
+function initialize() {
+  var wtu = WebGLTestUtils;
+  var canvas = document.getElementById("canvas");
+  var gl1 = wtu.create3DContext(canvas);
+  if (!gl1) {
+    testFailed("WebGL context does not exist");
+    finishTest();
+  } else {
+    testPassed("WebGL context exists");
+    gl1.myProperty = 2;
+    wtu.requestAnimFrame(runTest);
+  }
+}
+
+function runTest() {
+  webglHarnessCollectGarbage();
+  var wtu = WebGLTestUtils;
+  var canvas = document.getElementById("canvas");
+  gl2 = wtu.create3DContext(canvas);
+  shouldBe('gl2.myProperty', '2');
+  finishTest();
+}
+</script>
+</body>
+</html>
diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/context/zero-sized-canvas.html b/dom/canvas/test/webgl-conf/checkout/conformance/context/zero-sized-canvas.html
new file mode 100644
index 0000000000..13e1338865
--- /dev/null
+++ b/dom/canvas/test/webgl-conf/checkout/conformance/context/zero-sized-canvas.html
@@ -0,0 +1,59 @@
+<!--
+Copyright (c) 2020 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>
+<div id="description"></div>
+<div id="console"></div>
+<script>
+"use strict";
+
+// Global declarations so that "shouldBe" can eval with them:
+let gl;
+
+(function() {
+    description('Check that zero-sized canvases work with WebGL.');
+
+    testZero();
+
+    finishTest();
+})();
+
+function testZero() {
+    const canvas = document.createElement('canvas');
+    canvas.width = 0;
+    canvas.height = 0;
+    gl = WebGLTestUtils.create3DContext(canvas);
+
+    expectTrue(gl, `Context creation with ${canvas.width}x${canvas.height} canvas should succeed.`);
+    shouldBe('gl.drawingBufferWidth', '1');
+    shouldBe('gl.drawingBufferHeight', '1');
+    shouldBeFalse('gl.isContextLost()');
+
+    const version = gl.getParameter(gl.VERSION);
+    expectTrue(version && version.length, `getParameter() should return something.`);
+
+    debug('canvas.width = 2');
+    canvas.width = 2;
+    shouldBe('gl.drawingBufferWidth', '2');
+    shouldBeFalse('gl.isContextLost()');
+
+    debug('canvas.width = 0');
+    canvas.width = 0;
+    shouldBe('gl.drawingBufferWidth', '1');
+    shouldBeFalse('gl.isContextLost()');
+}
+
+</script>
+</body>
+</html>
-- 
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