Convert //cc from scoped_ptr to std::unique_ptr.

cc/trees/layer_tree_host_pixeltest_tiles.cc

Index: cc/trees/layer_tree_host_pixeltest_tiles.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_tiles.cc b/cc/trees/layer_tree_host_pixeltest_tiles.cc
index 764e37dcf20a15a026d11f684e88d912c5ab8665..292c3edfc7edd2c5e4cf74754439c9e8acfceb07 100644
--- a/cc/trees/layer_tree_host_pixeltest_tiles.cc
+++ b/cc/trees/layer_tree_host_pixeltest_tiles.cc
@@ -98,7 +98,7 @@ class LayerTreeHostTilesPixelTest : public LayerTreePixelTest {
   }
 
   base::FilePath ref_file_;
-  scoped_ptr<SkBitmap> result_bitmap_;
+  std::unique_ptr<SkBitmap> result_bitmap_;
   RasterMode raster_mode_;
 };