Change X11 error handler override to allow easy X11 error checking.

gpu/command_buffer/common/gl_mock.h

Index: gpu/command_buffer/common/gl_mock.h
diff --git a/gpu/command_buffer/common/gl_mock.h b/gpu/command_buffer/common/gl_mock.h
index 4c5c11475f82dec117409de2b71670a13ec4a2da..29fb0000c5e1247313997d3ac00209c76cde1f04 100644
--- a/gpu/command_buffer/common/gl_mock.h
+++ b/gpu/command_buffer/common/gl_mock.h
@@ -9,6 +9,11 @@
 #define GPU_COMMAND_BUFFER_COMMON_GL_MOCK_H_
 #pragma once
 
+// Include gtest.h out of order because <X11/X.h> #define's Bool & None, which
+// gtest uses as struct names (inside a namespace).  This means that
+// #include'ing gtest after anything that pulls in X.h fails to compile.
+// This is http://code.google.com/p/googletest/issues/detail?id=371
+#include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "ui/gfx/gl/gl_interface.h"
 
@@ -450,4 +455,3 @@ class MockGLInterface : public GLInterface {
 }  // namespace gfx
 
 #endif  // GPU_COMMAND_BUFFER_COMMON_GL_MOCK_H_
-