[#3] Pass gfx structs by const ref (gfx::SizeF)

cc/trees/layer_tree_host_impl_unittest.cc

 // Copyright 2011 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/trees/layer_tree_host_impl.h"
 
 #include <cmath>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 2459 matching lines @@
   virtual gfx::Vector2dF GetTotalScrollOffset() OVERRIDE {
     return getter_return_value_;
   }
 
   virtual bool IsExternalFlingActive() const OVERRIDE { return false; }
 
   virtual void SetTotalPageScaleFactor(float page_scale_factor) OVERRIDE {
     page_scale_factor_ = page_scale_factor;
   }
 
-  virtual void SetScrollableSize(gfx::SizeF scrollable_size) OVERRIDE {
+  virtual void SetScrollableSize(const gfx::SizeF& scrollable_size) OVERRIDE {
     scrollable_size_ = scrollable_size;
   }
 
   gfx::Vector2dF last_set_scroll_offset() {
     return last_set_scroll_offset_;
   }
 
   void set_getter_return_value(gfx::Vector2dF value) {
     getter_return_value_ = value;
   }
@@ skipping 2944 matching lines @@
                                      &set_needs_redraw_count));
     // Empty damage rect won't signal the monitor.
     host_impl_->SetNeedsRedrawRect(gfx::Rect());
     EXPECT_EQ(0, set_needs_commit_count);
     EXPECT_EQ(2, set_needs_redraw_count);
   }
 }
 
 }  // namespace
 }  // namespace cc