Add a stat to the smoothness benchmark for avg number of missing tiles.

cc/rendering_stats.cc

 // Copyright 2012 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.
 
 #include "cc/rendering_stats.h"
 
 namespace cc {
 
 RenderingStats::RenderingStats()
     : numAnimationFrames(0),
       numFramesSentToScreen(0),
       droppedFrameCount(0),
       totalPaintTimeInSeconds(0),
       totalRasterizeTimeInSeconds(0),
       totalCommitTimeInSeconds(0),
       totalCommitCount(0),
       totalPixelsPainted(0),
       totalPixelsRasterized(0),
       numImplThreadScrolls(0),
       numMainThreadScrolls(0),
-      numLayersDrawn(0) {
+      numLayersDrawn(0),
+      numMissingTiles(0) {
 }
 
 void RenderingStats::EnumerateFields(Enumerator* enumerator) const {
     enumerator->AddInt64("numAnimationFrames", numAnimationFrames);
     enumerator->AddInt64("numFramesSentToScreen", numFramesSentToScreen);
     enumerator->AddInt64("droppedFrameCount", droppedFrameCount);
     enumerator->AddDouble("totalPaintTimeInSeconds", totalPaintTimeInSeconds);
     enumerator->AddDouble("totalRasterizeTimeInSeconds",
                           totalRasterizeTimeInSeconds);
     enumerator->AddDouble("totalCommitTimeInSeconds", totalCommitTimeInSeconds);
     enumerator->AddInt64("totalCommitCount", totalCommitCount);
     enumerator->AddInt64("totalPixelsPainted", totalPixelsPainted);
     enumerator->AddInt64("totalPixelsRasterized", totalPixelsRasterized);
     enumerator->AddInt64("numImplThreadScrolls", numImplThreadScrolls);
     enumerator->AddInt64("numMainThreadScrolls", numMainThreadScrolls);
     enumerator->AddInt64("numLayersDrawn", numLayersDrawn);
+    enumerator->AddInt64("numMissingTiles", numMissingTiles);
 }
 
 }  // namespace cc