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

cc/trees/layer_tree_host_unittest_scroll.cc

Index: cc/trees/layer_tree_host_unittest_scroll.cc
diff --git a/cc/trees/layer_tree_host_unittest_scroll.cc b/cc/trees/layer_tree_host_unittest_scroll.cc
index 52bcaf94ad89b7e2c069cf0acb46b618807888f6..cf2ac87e181ec89467b7c3276d25517a3466fffe 100644
--- a/cc/trees/layer_tree_host_unittest_scroll.cc
+++ b/cc/trees/layer_tree_host_unittest_scroll.cc
@@ -83,7 +83,7 @@ class LayerTreeHostScrollTestScrollSimple : public LayerTreeHostScrollTest {
     }
   }
 
-  virtual void ApplyScrollAndScale(gfx::Vector2d scroll_delta,
+  virtual void ApplyScrollAndScale(const gfx::Vector2d& scroll_delta,
                                    float scale) OVERRIDE {
     num_scrolls_++;
   }
@@ -167,7 +167,7 @@ class LayerTreeHostScrollTestScrollMultipleRedraw
     }
   }
 
-  virtual void ApplyScrollAndScale(gfx::Vector2d scroll_delta,
+  virtual void ApplyScrollAndScale(const gfx::Vector2d& scroll_delta,
                                    float scale) OVERRIDE {
     num_scrolls_++;
   }
@@ -331,7 +331,7 @@ class LayerTreeHostScrollTestScrollAbortedCommit
     }
   }
 
-  virtual void ApplyScrollAndScale(gfx::Vector2d scroll_delta,
+  virtual void ApplyScrollAndScale(const gfx::Vector2d& scroll_delta,
                                    float scale) OVERRIDE {
     num_impl_scrolls_++;
   }
@@ -504,7 +504,7 @@ class LayerTreeHostScrollTestCaseWithChild : public LayerTreeHostScrollTest {
     final_scroll_offset_ = expected_scroll_layer_->scroll_offset();
   }
 
-  virtual void ApplyScrollAndScale(gfx::Vector2d scroll_delta,
+  virtual void ApplyScrollAndScale(const gfx::Vector2d& scroll_delta,
                                    float scale) OVERRIDE {
     num_scrolls_++;
   }
@@ -864,7 +864,7 @@ class ImplSidePaintingScrollTestSimple : public ImplSidePaintingScrollTest {
     }
   }
 
-  virtual void ApplyScrollAndScale(gfx::Vector2d scroll_delta,
+  virtual void ApplyScrollAndScale(const gfx::Vector2d& scroll_delta,
                                    float scale) OVERRIDE {
     num_scrolls_++;
   }