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

webkit/renderer/compositor_bindings/scrollbar_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webkit/renderer/compositor_bindings/scrollbar_impl.h"
 
 #include "base/logging.h"
 #include "third_party/WebKit/public/platform/WebScrollbar.h"
 #include "third_party/WebKit/public/platform/WebScrollbarThemeGeometry.h"
 
@@ skipping 45 matching lines @@
   if (scrollbar_->orientation() == WebScrollbar::Horizontal)
     return thumb_rect.width();
   return thumb_rect.height();
 }
 
 gfx::Rect ScrollbarImpl::TrackRect() const {
   return geometry_->trackRect(scrollbar_.get());
 }
 
 void ScrollbarImpl::PaintPart(
-    SkCanvas* canvas, cc::ScrollbarPart part, gfx::Rect content_rect) {
+    SkCanvas* canvas, cc::ScrollbarPart part,
+    const gfx::Rect& content_rect) {
   if (part == cc::THUMB) {
     painter_.paintThumb(canvas, content_rect);
     return;
   }
 
   // The following is a simplification of ScrollbarThemeComposite::paint.
   painter_.paintScrollbarBackground(canvas, content_rect);
 
   if (geometry_->hasButtons(scrollbar_.get())) {
     gfx::Rect back_button_start_paint_rect =
@@ skipping 20 matching lines @@
   bool thumb_present = geometry_->hasThumb(scrollbar_.get());
   if (thumb_present) {
     painter_.paintForwardTrackPart(canvas, track_paint_rect);
     painter_.paintBackTrackPart(canvas, track_paint_rect);
   }
 
   painter_.paintTickmarks(canvas, track_paint_rect);
 }
 
 }  // namespace webkit