Unit tests have been created for the GPUTiming.

ui/gl/gpu_timing.cc

Index: ui/gl/gpu_timing.cc
diff --git a/ui/gl/gpu_timing.cc b/ui/gl/gpu_timing.cc
index 01a0e192e005ad44c84efe3599bbe6550d0015e9..dc720df58e03774b20fbe027460497a9b1d32cb1 100644
--- a/ui/gl/gpu_timing.cc
+++ b/ui/gl/gpu_timing.cc
@@ -52,7 +52,7 @@ int64 GPUTiming::CalculateTimerOffset(base::Callback<int64(void)> cpu_time) {
       int64 now =
           cpu_time.is_null()
           ? (base::TraceTicks::Now() - base::TraceTicks()).InMicroseconds()
-              : cpu_time.Run();
+          : cpu_time.Run();
       offset_ = now - gl_now / base::Time::kNanosecondsPerMicrosecond;
       offset_valid_ = (timer_type_ == kTimerTypeARB);
     } else {
@@ -251,6 +251,12 @@ void GPUTimingClient::SetCpuTimeForTesting(
   cpu_time_for_testing_ = cpu_time;
 }
 
+int64 GPUTimingClient::GetCurrentCPUTime() {
+  return cpu_time_for_testing_.is_null()
+         ? (base::TraceTicks::Now() - base::TraceTicks()).InMicroseconds()
+         : cpu_time_for_testing_.Run();
+}
+
 GPUTimingClient::~GPUTimingClient() {
 }