Output stacktraces on WebGL conformance failure.

content/test/gpu/gpu_tests/webgl_conformance.py

 # Copyright (c) 2012 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.
 import os
 
 from gpu_tests import gpu_test_base
 from gpu_tests import path_util
 from gpu_tests import webgl_conformance_expectations
 from gpu_tests import webgl2_conformance_expectations
 
@@ skipping 66 matching lines @@
            test_path.replace('/', '_').replace('-', '_').
            replace('\\', '_').rpartition('.')[0].replace('.', '_'))
 
 
 class WebglConformanceValidator(gpu_test_base.ValidatorBase):
   def __init__(self):
     super(WebglConformanceValidator, self).__init__()
 
   def ValidateAndMeasurePage(self, page, tab, results):
     if not _DidWebGLTestSucceed(tab):
-      raise page_test.Failure(_WebGLTestMessages(tab))
+      is_valid_dump, trace_output = tab.browser.GetStackTrace()

[Ken Russell (switch to Gerrit), 2016/06/16 17:48:01]

I was concerned about the performance cost of doing this after every page run
but realize that this will only be executed after a failure, which should not be
the common case.

+      messages = _WebGLTestMessages(tab)
+      if is_valid_dump:
+        messages += '\nStack Trace:\n' + trace_output
+      raise page_test.Failure(messages)
 
   def CustomizeBrowserOptions(self, options):
     # --test-type=gpu is used only to suppress the "Google API Keys are missing"
     # infobar, which causes flakiness in tests.
     options.AppendExtraBrowserArgs([
         '--disable-gesture-requirement-for-media-playback',
         '--disable-domain-blocking-for-3d-apis',
         '--disable-gpu-process-crash-limit',
         '--js-flags=--expose-gc',
         '--test-type=gpu',
@@ skipping 245 matching lines @@
           # We only check min-version >= 2.0.0 for the top level list.
           test_paths += WebglConformance._ParseTests(
               include_path, version, webgl2_only, min_version_to_compare)
         else:
           test = os.path.join(current_dir, test_name)
           if webgl_version > 1:
             test += '?webglVersion=' + str(webgl_version)
           test_paths.append(test)
 
     return test_paths