cc: Add tiling raster tile iterators.

cc/resources/managed_tile_state.h

Index: cc/resources/managed_tile_state.h
diff --git a/cc/resources/managed_tile_state.h b/cc/resources/managed_tile_state.h
index 644562309f0446a8ca29b6396348f462d56970ba..e4579833829d992308512b6e4fe1a1c9fb016794 100644
--- a/cc/resources/managed_tile_state.h
+++ b/cc/resources/managed_tile_state.h
@@ -69,10 +69,15 @@ class CC_EXPORT ManagedTileState {
       return mode_ == RESOURCE_MODE || mode_ == PICTURE_PILE_MODE;
     }
 
+    inline bool has_resource() const { return !!resource_; }
+
     size_t GPUMemoryUsageInBytes() const;
 
     void SetSolidColorForTesting(SkColor color) { set_solid_color(color); }
     void SetHasTextForTesting(bool has_text) { has_text_ = has_text; }
+    void SetResourceForTesting(scoped_ptr<ScopedResource> resource) {
+      resource_ = resource.Pass();
+    }
 
    private:
     friend class TileManager;