gpu: Fix some context lost marking glitches+leaks and add UMA stats

gpu/command_buffer/service/gl_context_mock.h

+// Copyright 2015 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.
+
+#ifndef GPU_COMMAND_BUFFER_SERVICE_GL_CONTEXT_MOCK_H_
+#define GPU_COMMAND_BUFFER_SERVICE_GL_CONTEXT_MOCK_H_
+
+#include "testing/gmock/include/gmock/gmock.h"
+#include "ui/gl/gl_context_stub_with_extensions.h"
+
+namespace gpu {
+
+class GLContextMock : public gfx::GLContextStubWithExtensions {
+ public:
+  GLContextMock();
+
+  MOCK_METHOD1(MakeCurrent, bool(gfx::GLSurface* surface));
+
+ protected:
+  virtual ~GLContextMock();
+};
+
+}  // namespace gpu
+
+#endif  // GPU_COMMAND_BUFFER_SERVICE_GL_CONTEXT_MOCK_H_