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 70c465c1530cce2d5da9872dd530db17e1e0d3c3..ee3a51ee77143e89709068e4b244dd1827a54564 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,