cc: Add predictive pre-painting.

cc/tiled_layer.h

Index: cc/tiled_layer.h
diff --git a/cc/tiled_layer.h b/cc/tiled_layer.h
index 616339129e9bbcf7c5d2fc24286bd85fd43e8b69..cc2c97d8485d9b3e94d5f46e818ec100767c6b0e 100644
--- a/cc/tiled_layer.h
+++ b/cc/tiled_layer.h
@@ -84,6 +84,7 @@ private:
     bool haveTexturesForTiles(int left, int top, int right, int bottom, bool ignoreOcclusions);
     IntRect markTilesForUpdate(int left, int top, int right, int bottom, bool ignoreOcclusions);
     void updateTileTextures(const IntRect& paintRect, int left, int top, int right, int bottom, CCTextureUpdateQueue&, const CCOcclusionTracker*, CCRenderingStats&);
+    void updateScrollPrediction();
 
     UpdatableTile* tileAt(int, int) const;
     UpdatableTile* createTile(int, int);
@@ -93,6 +94,12 @@ private:
     bool m_failedUpdate;
     LayerTextureUpdater::SampledTexelFormat m_sampledTexelFormat;
 
+    // Used for predictive painting.
+    IntSize m_predictedScroll;
+    IntRect m_predictedVisibleRect;
+    IntRect m_previousVisibleRect;
+    IntSize m_previousContentBounds;
+
     TilingOption m_tilingOption;
     scoped_ptr<CCLayerTilingData> m_tiler;
 };