improving UI of FPS counter

cc/frame_rate_counter.h

Index: cc/frame_rate_counter.h
diff --git a/cc/frame_rate_counter.h b/cc/frame_rate_counter.h
index a0e3a19d53894cdbe06d782f2c0b75edbe79e3c9..faf82db59332a945c8577a5392be6e47388637da 100644
--- a/cc/frame_rate_counter.h
+++ b/cc/frame_rate_counter.h
@@ -12,7 +12,7 @@
 namespace cc {
 
 // This class maintains a history of timestamps, and provides functionality to
-// intelligently compute average frames per second (and standard deviation).
+// intelligently compute average frames per second.
 class FrameRateCounter {
 public:
     static scoped_ptr<FrameRateCounter> create(bool hasImplThread);
@@ -20,7 +20,7 @@ public:
     void markBeginningOfFrame(base::TimeTicks timestamp);
     void markEndOfFrame();
     int currentFrameNumber() const { return m_currentFrameNumber; }
-    void getAverageFPSAndStandardDeviation(double& averageFPS, double& standardDeviation) const;
+    double getAverageFPS() const;
     int timeStampHistorySize() const { return kTimeStampHistorySize; }
 
     // n = 0 returns the oldest frame retained in the history,