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diff --git a/dom/canvas/test/webgl-conf/checkout/conformance/glsl/bugs/pow-of-small-constant-in-user-defined-function.html b/dom/canvas/test/webgl-conf/checkout/conformance/glsl/bugs/pow-of-small-constant-in-user-defined-function.html
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+++ b/dom/canvas/test/webgl-conf/checkout/conformance/glsl/bugs/pow-of-small-constant-in-user-defined-function.html
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+<!--
+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>Bug - calculating powers of constants smaller than 1.0e-5 in user-defined functions should work</title>
+<link rel="stylesheet" href="../../../resources/js-test-style.css"/>
+<script src="../../../js/js-test-pre.js"></script>
+<script src="../../../js/webgl-test-utils.js"></script>
+</head>
+<body>
+<canvas id="canvas" width="256" height="256"> </canvas>
+<div id="description"></div>
+<div id="console"></div>
+<script id="vshader" type="x-shader/x-vertex">
+attribute vec3 aPosition;
+
+void main() {
+    gl_Position = vec4(aPosition, 1);
+}
+</script>
+<script id="fshader" type="x-shader/x-fragment">
+precision highp float;
+
+float fun(float arg) {
+    // These values are still easily within the highp range.
+    // The minimum range in terms of 10's exponent is around -19 to 19, and IEEE-754 single precision range is higher than that.
+    return 1.0e12 * pow(arg, 2.0);
+}
+
+void main() {
+    // Note that the bug did not reproduce if an uniform was passed to the function instead of a constant,
+    // or if the expression was moved outside the user-defined function.
+    const float a = 1.0e-6;
+    float b = fun(a);
+    if (abs(b - 1.0) < 0.01) {
+        gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0); // green
+    } else {
+        gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0); // red
+    }
+}
+</script>
+<script type="application/javascript">
+"use strict";
+description();
+debug("");
+var wtu = WebGLTestUtils;
+function test() {
+  var gl = wtu.create3DContext("canvas");
+  if (!gl) {
+    testFailed("context does not exist");
+    return;
+  }
+  if (gl.getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_FLOAT).precision == 0) {
+    testPassed("highp precision not supported");
+  } else {
+    wtu.setupUnitQuad(gl);
+    var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["aPosition"], undefined, true);
+    wtu.drawUnitQuad(gl);
+    wtu.checkCanvasRect(gl, 0, 0, 256, 256, [0, 255, 0, 255]);
+  }
+};
+
+test();
+finishTest();
+</script>
+</body>
+</html>
+