gpu: Add WebGL robustness telemetry test

content/test/gpu/gpu_tests/webgl_robustness.py

+# Copyright (c) 2013 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.
+from telemetry import test
+from telemetry.page import page_set
+from webgl_conformance import WebglConformanceValidator
+from webgl_conformance import conformance_harness_script
+from webgl_conformance import conformance_path
+
+
+robustness_harness_script = conformance_harness_script + r"""
+  window.confirm = function() {
+    var canvas = document.getElementById('example');
+    canvas.addEventListener('webglcontextlost', function() {
+      webglTestHarness.notifyFinished();

[Ken Russell (switch to Gerrit), 2013/07/30 19:39:27]

If the GPU happens to be fast enough to run that test without losing the
context, won't the test be considered to fail?

[bajones, 2013/07/30 20:51:03]

Yeah, I worry that this is a race condition as well. The test you are using does
several fairly slow operations, but it's still possible that they could complete
pretty quickly. It would be better to have the script spin in a
requestAnimationFrame or similar loop at the end to ensure it doesn't exit too
quickly.

+    });
+    return true;
+  }
+"""
+
+
+class WebglRobustness(test.Test):
+  enabled = False
+  test = WebglConformanceValidator
+
+  def CreatePageSet(self, options):
+    page_set_dict = {
+      'description': 'Test cases for WebGL robustness',

[Ken Russell (switch to Gerrit), 2013/07/30 19:39:27]

Just checking: this test won't be run by default, will it? The concern is
running it on devices which don't support the robustness extension.

+      'user_agent_type': 'desktop',
+      'serving_dirs': [''],
+      'pages': [
+        {
+          'url': 'file:///extra/lots-of-polys-example.html',

[bajones, 2013/07/30 20:51:03]

Perhaps I'm missing something, but I don't see where this triggers a context
loss. If this script is triggering a context loss spontaneously that sounds like
a bug and we shouldn't be relying on it in tests.

Would it be reasonable to use the WEBGL_lose_context extension instead?
http://www.khronos.org/registry/webgl/extensions/WEBGL_lose_context/

+          'script_to_evaluate_on_commit': robustness_harness_script,
+          'wait_for_javascript_expression': 'webglTestHarness._finished'
+        }
+      ]
+    }
+    return page_set.PageSet.FromDict(page_set_dict, conformance_path)