cc: Rework tiling set eviction iterator.

cc/resources/picture_layer_tiling_set.h

Index: cc/resources/picture_layer_tiling_set.h
diff --git a/cc/resources/picture_layer_tiling_set.h b/cc/resources/picture_layer_tiling_set.h
index 24da44d0f977664355eb7bf6b6190c2d31b0692b..c8383c858a614ae4dc5169a28bb480439c94e913 100644
--- a/cc/resources/picture_layer_tiling_set.h
+++ b/cc/resources/picture_layer_tiling_set.h
@@ -31,10 +31,10 @@ class CC_EXPORT PictureLayerTilingSet {
     LOWER_THAN_LOW_RES
   };
   struct TilingRange {
-    TilingRange(size_t start, size_t end) : start(start), end(end) {}
+    TilingRange(int start, int end) : start(start), end(end) {}
 
-    size_t start;
-    size_t end;
+    int start;
+    int end;
   };
 
   static scoped_ptr<PictureLayerTilingSet> Create(