[#2] Pass gfx structs by const ref (gfx::Rect, gfx::RectF)

cc/resources/raster_worker_pool.cc

Index: cc/resources/raster_worker_pool.cc
diff --git a/cc/resources/raster_worker_pool.cc b/cc/resources/raster_worker_pool.cc
index b017038ba53f572523c255e59c1623ce6a9a89c7..2871f65f718e5fc0bac800ad5011203513ca7ede 100644
--- a/cc/resources/raster_worker_pool.cc
+++ b/cc/resources/raster_worker_pool.cc
@@ -54,7 +54,7 @@ class RasterWorkerPoolTaskImpl : public internal::RasterWorkerPoolTask {
  public:
   RasterWorkerPoolTaskImpl(const Resource* resource,
                            PicturePileImpl* picture_pile,
-                           gfx::Rect content_rect,
+                           const gfx::Rect& content_rect,
                            float contents_scale,
                            RasterMode raster_mode,
                            TileResolution tile_resolution,
@@ -468,7 +468,7 @@ RasterWorkerPool::RasterTask::~RasterTask() {
 RasterWorkerPool::RasterTask RasterWorkerPool::CreateRasterTask(
     const Resource* resource,
     PicturePileImpl* picture_pile,
-    gfx::Rect content_rect,
+    const gfx::Rect& content_rect,
     float contents_scale,
     RasterMode raster_mode,
     TileResolution tile_resolution,