[#6]Pass gfx structs by const ref (gfx::Vector2d)

cc/trees/layer_tree_host_impl.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 <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 410 matching lines @@
                                 &memory_nice_to_have_bytes,
                                 &memory_allocated_bytes,
                                 &memory_used_bytes);
   SendManagedMemoryStats(memory_required_bytes,
                          memory_nice_to_have_bytes,
                          memory_used_bytes);
 
   client_->DidManageTiles();
 }
 
-void LayerTreeHostImpl::StartPageScaleAnimation(gfx::Vector2d target_offset,
-                                                bool anchor_point,
-                                                float page_scale,
-                                                base::TimeDelta duration) {
+void LayerTreeHostImpl::StartPageScaleAnimation(
+    const gfx::Vector2d& target_offset,
+    bool anchor_point,
+    float page_scale,
+    base::TimeDelta duration) {
   if (!RootScrollLayer())
     return;
 
   gfx::Vector2dF scroll_total =
       RootScrollLayer()->scroll_offset() + RootScrollLayer()->ScrollDelta();
   gfx::SizeF scaled_scrollable_size = active_tree_->ScrollableSize();
   gfx::SizeF viewport_size = UnscaledScrollableViewportSize();
 
   // Easing constants experimentally determined.
   scoped_ptr<TimingFunction> timing_function =
@@ skipping 2477 matching lines @@
   swap_promise_monitor_.erase(monitor);
 }
 
 void LayerTreeHostImpl::NotifySwapPromiseMonitorsOfSetNeedsRedraw() {
   std::set<SwapPromiseMonitor*>::iterator it = swap_promise_monitor_.begin();
   for (; it != swap_promise_monitor_.end(); it++)
     (*it)->OnSetNeedsRedrawOnImpl();
 }
 
 }  // namespace cc