cc: Fixed computation of dropped frames.

tools/perf/metrics/smoothness.js

 // Copyright 2013 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.
 
 'use strict';
 
 /**
  * @fileoverview This file provides the RenderingStats object, used
  * to characterize rendering smoothness.
  */
@@ skipping 131 matching lines @@
   RafRenderingStats.prototype.recordFrameTime_ = function(timestamp) {
     if (!this.recording_)
       return;
 
     this.frameTimes_.push(timestamp);
     requestAnimationFrame(this.recordFrameTime_.bind(this));
   };
 
   RafRenderingStats.prototype.getDroppedFrameCount_ = function(frameTimes) {
     var droppedFrameCount = 0;
+    var droppedFrameThreshold = 1000 / 55;
     for (var i = 1; i < frameTimes.length; i++) {
       var frameTime = frameTimes[i] - frameTimes[i-1];
-      if (frameTime > 1000 / 55)
-        droppedFrameCount++;
+      if (frameTime > droppedFrameThreshold)
+        droppedFrameCount += Math.floor(frameTime / droppedFrameThreshold);
     }
     return droppedFrameCount;
   };
 
   function RenderingStats() {
     if (window.chrome && chrome.gpuBenchmarking &&
         chrome.gpuBenchmarking.renderingStats) {
       return new GpuBenchmarkingRenderingStats();
     }
     return new RafRenderingStats();
   }
 
   window.__RenderingStats = RenderingStats;
 })();