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 4681889ed3b06ea26d82c962eb7c3c6bc1dd77d2..a6cea6abb27c6c86d57f188e4418e5e65bf940a6 100644
--- a/cc/tiled_layer.h
+++ b/cc/tiled_layer.h
@@ -83,6 +83,7 @@ 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, TextureUpdateQueue&, const OcclusionTracker*, RenderingStats&);
+    void updateScrollPrediction();
 
     UpdatableTile* tileAt(int, int) const;
     UpdatableTile* createTile(int, int);
@@ -91,6 +92,12 @@ private:
     bool m_skipsDraw;
     bool m_failedUpdate;
 
+    // Used for predictive painting.
+    IntSize m_predictedScroll;
+    IntRect m_predictedVisibleRect;
+    IntRect m_previousVisibleRect;
+    IntSize m_previousContentBounds;
+
     TilingOption m_tilingOption;
     scoped_ptr<LayerTilingData> m_tiler;
 };