cc: Don't pass simple well-defined classes by reference.

cc/resources/picture.cc

 // Copyright 2012 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/resources/picture.h"
 
 #include "base/base64.h"
 #include "base/debug/trace_event.h"
 #include "cc/debug/rendering_stats.h"
 #include "cc/layers/content_layer_client.h"
@@ skipping 189 matching lines @@
   canvas->clipRect(gfx::RectToSkRect(content_rect));
   canvas->scale(contents_scale, contents_scale);
   canvas->translate(layer_rect_.x(), layer_rect_.y());
   // Pictures by default have LCD text enabled.
   if (!enable_lcd_text)
     canvas->setDrawFilter(&disable_lcd_text_filter);
   canvas->drawPicture(*picture_);
   canvas->restore();
 }
 
-void Picture::GatherPixelRefs(const gfx::Rect& layer_rect,
+void Picture::GatherPixelRefs(gfx::Rect layer_rect,
                               std::list<skia::LazyPixelRef*>& pixel_ref_list) {
   DCHECK(picture_);
   SkData* pixel_refs = SkPictureUtils::GatherPixelRefs(
       picture_.get(), SkRect::MakeXYWH(layer_rect.x(),
                                        layer_rect.y(),
                                        layer_rect.width(),
                                        layer_rect.height()));
   if (!pixel_refs)
     return;
 
@@ skipping 35 matching lines @@
 
   // Encode the picture as base64.
   size_t serialized_size = stream.bytesWritten();
   scoped_ptr<char[]> serialized_picture(new char[serialized_size]);
   stream.copyTo(serialized_picture.get());
   base::Base64Encode(std::string(serialized_picture.get(), serialized_size),
                      output);
 }
 
 }  // namespace cc