Unit tests have been created for the GPUTiming.

ui/gl/gpu_timing.h

 // Copyright (c) 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 UI_GL_GPU_TIMING_H_
 #define UI_GL_GPU_TIMING_H_
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gl/gl_export.h"
@@ skipping 112 matching lines @@
 
   // CheckAndResetTimerErrors has to be called before reading timestamps
   // from GPUTimers instances and after making sure all the timers
   // were available.
   // If the returned value is false, all the previous timers should be
   // discarded.
   bool CheckAndResetTimerErrors();
   void InvalidateTimerOffset();
 
   void SetCpuTimeForTesting(const base::Callback<int64(void)>& cpu_time);
+  int64 GetCurrentCPUTime();
 
  private:
   friend class base::RefCounted<GPUTimingClient>;
   friend class GPUTimer;
   friend class GPUTiming;
 
   virtual ~GPUTimingClient();
 
   // Returns the offset between the current gpu time and the cpu time.
   int64 CalculateTimerOffset();
 
   GPUTiming* gpu_timing_;
   GPUTiming::TimerType timer_type_ = GPUTiming::kTimerTypeInvalid;
   uint32_t disjoint_counter_ = 0;
   base::Callback<int64(void)> cpu_time_for_testing_;
 
   DISALLOW_COPY_AND_ASSIGN(GPUTimingClient);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GPU_TIMING_H_