diff --git a/content/canvas/test/webgl/non-conf-tests/mochitest.ini b/content/canvas/test/webgl/non-conf-tests/mochitest.ini
index 22642249b07..fbe9d6c4035 100644
--- a/content/canvas/test/webgl/non-conf-tests/mochitest.ini
+++ b/content/canvas/test/webgl/non-conf-tests/mochitest.ini
@@ -3,6 +3,7 @@ support-files =
   driver-info.js
   webgl-util.js
 
+[test_highp_fs.html]
 [test_webgl_available.html]
 [test_webgl_conformance.html]
 [test_webgl_request_mismatch.html]
diff --git a/content/canvas/test/webgl/non-conf-tests/test_highp_fs.html b/content/canvas/test/webgl/non-conf-tests/test_highp_fs.html
new file mode 100644
index 00000000000..165767da538
--- /dev/null
+++ b/content/canvas/test/webgl/non-conf-tests/test_highp_fs.html
@@ -0,0 +1,62 @@
+<!DOCTYPE HTML>
+<title>WebGL test: `highp` support</title>
+<script src="/MochiKit/MochiKit.js"></script>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<link rel="stylesheet" href="/tests/SimpleTest/test.css">
+<script src="driver-info.js"></script>
+<script src="webgl-util.js"></script>
+<script id="shader-vs" type="x-shader/x-vertex">
+
+void main(void) {
+  gl_Position = vec4(vec3(0.0), 1.0);
+}
+
+</script>
+<script id="shader-fs" type="x-shader/x-fragment">
+
+precision highp float;
+
+void main(void) {
+  gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
+}
+
+</script>
+<body>
+<canvas id="c"></canvas>
+<script>
+
+// Give ourselves a scope to return early from:
+(function() {
+  var gl = WebGLUtil.getWebGL('c');
+  if (!gl) {
+    todo(false, 'WebGL is unavailable.');
+    return;
+  }
+
+  // Catch actual WebGLUtil errors, not GL errors.
+  function errorFunc(str) {
+    ok(false, 'Error: ' + str);
+  }
+  WebGLUtil.setErrorFunc(errorFunc);
+
+  function checkGLError(func, info) {
+    var error = gl.getError();
+    var prefix = info ? ('[' + info + '] ') : ''
+    func(!error, prefix + 'gl.getError should be 0x0, was 0x' + error.toString(16) + '.');
+  }
+
+  var format = gl.getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_FLOAT);
+  var prog = WebGLUtil.createProgramByIds(gl, 'shader-vs', 'shader-fs');
+  checkGLError(ok);
+  
+  if (format) {
+    ok(prog, 'Frag shader with unconditional `precision highp float` should ' +
+             'link if `getShaderPrecisionFormat` gives a format for it.');
+  } else {
+    ok(!prog, 'Frag shader with unconditional `precision highp float` should ' +
+              'NOT link if `getShaderPrecisionFormat` gives NO format for it.');
+  }
+})();
+
+</script>
+
diff --git a/content/canvas/test/webgl/non-conf-tests/webgl-util.js b/content/canvas/test/webgl/non-conf-tests/webgl-util.js
index 9936f8e0c20..da29327048b 100644
--- a/content/canvas/test/webgl/non-conf-tests/webgl-util.js
+++ b/content/canvas/test/webgl/non-conf-tests/webgl-util.js
@@ -1,6 +1,6 @@
 WebGLUtil = (function() {
   // ---------------------------------------------------------------------------
-  // Error handling
+  // Error handling (for obvious failures, such as invalid element ids)
 
   function defaultErrorFunc(str) {
     console.log('Error: ' + str);
@@ -15,6 +15,22 @@ WebGLUtil = (function() {
     gErrorFunc(str);
   }
 
+  // ---------------------------------------------------------------------------
+  // Warning handling (for failures that may be intentional)
+
+  function defaultWarningFunc(str) {
+    console.log('Warning: ' + str);
+  }
+
+  var gWarningFunc = defaultWarningFunc;
+  function setWarningFunc(func) {
+    gWarningFunc = func;
+  }
+
+  function warning(str) {
+    gWarningFunc(str);
+  }
+
   // ---------------------------------------------------------------------------
   // WebGL helpers
 
@@ -63,19 +79,19 @@ WebGLUtil = (function() {
       return null;
     }
 
-    var src = getContentById(id);
+    var src = getContentFromElem(elem);
 
     var shader;
     if (elem.type == "x-shader/x-fragment") {
       shader = gl.createShader(gl.FRAGMENT_SHADER);
-    } else if (shaderScript.type == "x-shader/x-vertex") {
+    } else if (elem.type == "x-shader/x-vertex") {
       shader = gl.createShader(gl.VERTEX_SHADER);
     } else {
       error('Bad MIME type for shader \'' + id + '\': ' + elem.type + '.');
       return null;
     }
 
-    gl.shaderSource(shader, str);
+    gl.shaderSource(shader, src);
     gl.compileShader(shader);
 
     return shader;
@@ -93,11 +109,11 @@ WebGLUtil = (function() {
     gl.linkProgram(prog);
 
     if (!gl.getProgramParameter(prog, gl.LINK_STATUS)) {
-      var str = "Shader program linking failed:\n";
-      str += "Shader program info log:\n" + gl.getProgramInfoLog(prog) + "\n\n";
-      str += "Vert shader log:\n" + gl.getShaderInfoLog(vs) + "\n\n";
-      str += "Frag shader log:\n" + gl.getShaderInfoLog(fs);
-      error(str);
+      var str = "Shader program linking failed:";
+      str += "\nShader program info log:\n" + gl.getProgramInfoLog(prog);
+      str += "\n\nVert shader log:\n" + gl.getShaderInfoLog(vs);
+      str += "\n\nFrag shader log:\n" + gl.getShaderInfoLog(fs);
+      warning(str);
       return null;
     }
 
@@ -106,6 +122,7 @@ WebGLUtil = (function() {
 
   return {
     setErrorFunc: setErrorFunc,
+    setWarningFunc: setWarningFunc,
 
     getWebGL: getWebGL,
     createShaderById: createShaderById,
