WebGL expectations: add unittest checking pages exist.

content/test/gpu/gpu_tests/webgl_conformance_expectations.py

Index: content/test/gpu/gpu_tests/webgl_conformance_expectations.py
diff --git a/content/test/gpu/gpu_tests/webgl_conformance_expectations.py b/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
index 2968a3a980c0444781857b9ad477a5c846da4731..640976a8bed2b9243b3e7998db82b9d2a8332dc1 100644
--- a/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
+++ b/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
@@ -16,6 +16,11 @@ class WebGLConformanceExpectations(GpuTestExpectations):
     self.CheckPatternIsValid(pattern)
     GpuTestExpectations.Fail(self, pattern, condition, bug)
 
+  def Flaky(self, pattern, condition=None, bug=None, max_num_retries=2):
+    self.CheckPatternIsValid(pattern)
+    GpuTestExpectations.Flaky(self, pattern, condition, bug=bug,
+        max_num_retries=max_num_retries)
+
   def Skip(self, pattern, condition=None, bug=None):
     self.CheckPatternIsValid(pattern)
     GpuTestExpectations.Skip(self, pattern, condition, bug)