Add more WebGL pixel tests.

content/test/data/gpu/pixel_webgl_util.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // READ BEFORE UPDATING:
 // If this file is updated, make sure to increment the "revision" value of any
 // tests that use this file in content/test/gpu/page_sets/pixel_tests.py. This
 // will ensure that the baseline images are regenerated on the next run.
 
 var vertexShader = [
   "attribute vec3 pos;",
   "void main(void)",
   "{",
   "  gl_Position = vec4(pos, 1.0);",
   "}"
 ].join("\n");
 
 var fragmentShader = [
   "precision mediump float;",
   "void main(void)",
   "{",
   "  gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);",
   "}"
 ].join("\n");
 
-function initGL(canvas)
+function initGL(canvas, antialias, alpha)
 {
   var gl = null;
   try {
-    gl = canvas.getContext("experimental-webgl");
+    gl = canvas.getContext("experimental-webgl",
+                           {"alpha": alpha, "antialias":antialias});

[Ken Russell (switch to Gerrit), 2016/06/01 02:06:07]

Could you add a TODO about testing premultiplyAlpha as well? That's a key one
where testing coverage is missing.

[erikchen, 2016/06/01 17:07:03]

Done.

   } catch (e) {}
   if (!gl) {
     try {
       gl = canvas.getContext("webgl");
     } catch (e) { }
   }
   return gl;
 }
 
 function setupShader(gl, source, type) {
@@ skipping 45 matching lines @@
   gl.disable(gl.DEPTH_TEST);
   if (gl.getError() != gl.NO_ERROR)
     return false;
   return true;
 }
 
 function drawTriangle(gl) {
   gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
   gl.drawArrays(gl.TRIANGLES, 0, 3);
 }
+
+var g_swapsBeforeAckUtil = 15;
+var g_glUtil;
+
+function makeMain(antialias, alpha)
+{
+  return function() {
+    var canvas = document.getElementById("c");
+    g_glUtil = initGL(canvas, antialias, alpha);
+    if (g_glUtil && setup(g_glUtil)) {
+      drawSomeFramesUtil();
+    } else {
+      domAutomationController.setAutomationId(1);
+      domAutomationController.send("FAILURE");
+    }
+  };
+}
+
+function drawSomeFramesUtil()
+{
+  if (g_swapsBeforeAckUtil == 0) {
+    domAutomationController.setAutomationId(1);
+    domAutomationController.send("SUCCESS");
+  } else {
+    g_swapsBeforeAckUtil--;
+    drawTriangle(g_glUtil);
+    window.webkitRequestAnimationFrame(drawSomeFramesUtil);
+  }
+}