Revert of cc: Remove tile sharing from tilings.

cc/base/tiling_data.h

Index: cc/base/tiling_data.h
diff --git a/cc/base/tiling_data.h b/cc/base/tiling_data.h
index c95a6725b4886313ab8990ca5b26a31909738b35..a35be59f7484ccaacd51e32f8a7c9c626db4c2a7 100644
--- a/cc/base/tiling_data.h
+++ b/cc/base/tiling_data.h
@@ -132,7 +132,6 @@
   // with |consider| but which also do not intersect with |ignore|.
   class CC_EXPORT DifferenceIterator : public BaseDifferenceIterator {
    public:
-    DifferenceIterator();
     DifferenceIterator(const TilingData* tiling_data,
                        const gfx::Rect& consider_rect,
                        const gfx::Rect& ignore_rect);