cc: Add tiling raster tile iterators.

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 17274af142fd8a1001af3dfdfbfe21dd6c057daf..3a699ca872d51fcb6048938170db47d274027509 100644
--- a/cc/base/tiling_data.h
+++ b/cc/base/tiling_data.h
@@ -89,6 +89,7 @@ class CC_EXPORT TilingData {
   // Iterate through all indices whose bounds + border intersect with |rect|.
   class CC_EXPORT Iterator : public BaseIterator {
    public:
+    Iterator();
     Iterator(const TilingData* tiling_data, const gfx::Rect& tiling_rect);
     Iterator& operator++();
 
@@ -129,6 +130,7 @@ class CC_EXPORT TilingData {
   // order is a counterclockwise spiral around the given center.
   class CC_EXPORT SpiralDifferenceIterator : public BaseIterator {
    public:
+    SpiralDifferenceIterator();
     SpiralDifferenceIterator(const TilingData* tiling_data,
                              const gfx::Rect& consider_rect,
                              const gfx::Rect& ignore_rect,