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

cc/trees/occlusion_tracker.h

Index: cc/trees/occlusion_tracker.h
diff --git a/cc/trees/occlusion_tracker.h b/cc/trees/occlusion_tracker.h
index 68418c7e43533436881f397ed8ffbe2ce9e09120..85334bca2c19ec304bd4268b2801046103f01e1c 100644
--- a/cc/trees/occlusion_tracker.h
+++ b/cc/trees/occlusion_tracker.h
@@ -32,7 +32,7 @@ class RenderSurface;
 template <typename LayerType, typename RenderSurfaceType>
 class CC_EXPORT OcclusionTrackerBase {
  public:
-  OcclusionTrackerBase(gfx::Rect screen_space_clip_rect,
+  OcclusionTrackerBase(const gfx::Rect& screen_space_clip_rect,
                        bool record_metrics_for_frame);
   ~OcclusionTrackerBase();
 
@@ -48,7 +48,7 @@ class CC_EXPORT OcclusionTrackerBase {
   // |render_target| is the contributing layer's render target, and
   // |draw_transform| and |impl_draw_transform_is_unknown| are relative to that.
   bool Occluded(const LayerType* render_target,
-                gfx::Rect content_rect,
+                const gfx::Rect& content_rect,
                 const gfx::Transform& draw_transform,
                 bool impl_draw_transform_is_unknown) const;
 
@@ -58,7 +58,7 @@ class CC_EXPORT OcclusionTrackerBase {
   // |draw_transform| and |impl_draw_transform_is_unknown| are relative to that.
   gfx::Rect UnoccludedContentRect(
       const LayerType* render_target,
-      gfx::Rect content_rect,
+      const gfx::Rect& content_rect,
       const gfx::Transform& draw_transform,
       bool impl_draw_transform_is_unknown) const;
 
@@ -68,7 +68,7 @@ class CC_EXPORT OcclusionTrackerBase {
   gfx::Rect UnoccludedContributingSurfaceContentRect(
       const LayerType* layer,
       bool for_replica,
-      gfx::Rect content_rect) const;
+      const gfx::Rect& content_rect) const;
 
   // Report operations for recording overdraw metrics.
   OverdrawMetrics* overdraw_metrics() const {