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

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 161 matching lines @@
   }
 
   static void ExpectClearedScrollDeltasRecursive(LayerImpl* layer) {
     ASSERT_EQ(layer->ScrollDelta(), gfx::Vector2d());
     for (size_t i = 0; i < layer->children().size(); ++i)
       ExpectClearedScrollDeltasRecursive(layer->children()[i]);
   }
 
   static void ExpectContains(const ScrollAndScaleSet& scroll_info,
                              int id,
-                             gfx::Vector2d scroll_delta) {
+                             const gfx::Vector2d& scroll_delta) {
     int times_encountered = 0;
 
     for (size_t i = 0; i < scroll_info.scrolls.size(); ++i) {
       if (scroll_info.scrolls[i].layer_id != id)
         continue;
       EXPECT_VECTOR_EQ(scroll_delta, scroll_info.scrolls[i].scroll_delta);
       times_encountered++;
     }
 
     ASSERT_EQ(1, times_encountered);
@@ skipping 5575 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