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

cc/layers/painted_scrollbar_layer.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 "cc/layers/painted_scrollbar_layer.h"
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/layers/painted_scrollbar_layer_impl.h"
@@ skipping 130 matching lines @@
   // all of its associated resources.
   if (!host || host != layer_tree_host()) {
     track_resource_.reset();
     thumb_resource_.reset();
   }
 
   ContentsScalingLayer::SetLayerTreeHost(host);
 }
 
 gfx::Rect PaintedScrollbarLayer::ScrollbarLayerRectToContentRect(
-    gfx::Rect layer_rect) const {
+    const gfx::Rect& layer_rect) const {
   // Don't intersect with the bounds as in LayerRectToContentRect() because
   // layer_rect here might be in coordinates of the containing layer.
   gfx::Rect expanded_rect = gfx::ScaleToEnclosingRect(
       layer_rect, contents_scale_y(), contents_scale_y());
   // We should never return a rect bigger than the content_bounds().
   gfx::Size clamped_size = expanded_rect.size();
   clamped_size.SetToMin(content_bounds());
   expanded_rect.set_size(clamped_size);
   return expanded_rect;
 }
@@ skipping 48 matching lines @@
     thumb_resource_ = ScopedUIResource::Create(
         layer_tree_host(), RasterizeScrollbarPart(thumb_rect, THUMB));
   }
 
   // UI resources changed so push properties is needed.
   SetNeedsPushProperties();
   return true;
 }
 
 UIResourceBitmap PaintedScrollbarLayer::RasterizeScrollbarPart(
-    gfx::Rect rect,
+    const gfx::Rect& rect,
     ScrollbarPart part) {
   DCHECK(!rect.size().IsEmpty());
 
   SkBitmap skbitmap;
   skbitmap.setConfig(SkBitmap::kARGB_8888_Config, rect.width(), rect.height());
   skbitmap.allocPixels();
 
   SkCanvas skcanvas(skbitmap);
   skcanvas.translate(SkFloatToScalar(-rect.x()), SkFloatToScalar(-rect.y()));
   skcanvas.scale(SkFloatToScalar(contents_scale_x()),
@@ skipping 10 matching lines @@
 
   scrollbar_->PaintPart(&skcanvas, part, layer_rect);
   // Make sure that the pixels are no longer mutable to unavoid unnecessary
   // allocation and copying.
   skbitmap.setImmutable();
 
   return UIResourceBitmap(skbitmap);
 }
 
 }  // namespace cc