Abort ContextLost.WebGLContextLostFromQuantity if context creation fails.

content/test/gpu/gpu_tests/context_lost_expectations.py

Index: content/test/gpu/gpu_tests/context_lost_expectations.py
diff --git a/content/test/gpu/gpu_tests/context_lost_expectations.py b/content/test/gpu/gpu_tests/context_lost_expectations.py
index b207215d97a6bb10d602e9ae60a4fd1a8e520c3f..0f0c4f9457138e3a0b33ff4e2775a7b80e76c958 100644
--- a/content/test/gpu/gpu_tests/context_lost_expectations.py
+++ b/content/test/gpu/gpu_tests/context_lost_expectations.py
@@ -28,6 +28,12 @@ class ContextLostExpectations(GpuTestExpectations):
     self.Skip('ContextLost.WebGLContextLostFromSelectElement',
               ['win8', 'nvidia'], bug=524808)
 
+    # Flaky on Win x64 Debug bot.
+    # Unfortunately we can't identify this separately from the 32-bit bots.
+    # Try marking it flaky to see if this works around the problem.
+    self.Flaky('ContextLost.WebGLContextLostFromQuantity',
+               ['win', 'debug'], bug=628697)
+
     # Flaky on Mac 10.7 and 10.8 resulting in crashes during browser
     # startup, so skip this test in those configurations.
     self.Skip('ContextLost.WebGLContextLostFromSelectElement',