[#4] Pass gfx structs by const ref (gfx::PointF)

cc/layers/layer_position_constraint_unittest.cc

Index: cc/layers/layer_position_constraint_unittest.cc
diff --git a/cc/layers/layer_position_constraint_unittest.cc b/cc/layers/layer_position_constraint_unittest.cc
index 8f6dcb11798a5ba1153db4155931a7e8667f7df4..57e4c1de595b65c4dba6f7b0322d3b192830de10 100644
--- a/cc/layers/layer_position_constraint_unittest.cc
+++ b/cc/layers/layer_position_constraint_unittest.cc
@@ -19,8 +19,8 @@ namespace {
 void SetLayerPropertiesForTesting(LayerImpl* layer,
                                   const gfx::Transform& transform,
                                   const gfx::Transform& sublayer_transform,
-                                  gfx::PointF anchor,
-                                  gfx::PointF position,
+                                  const gfx::PointF& anchor,
+                                  const gfx::PointF& position,
                                   gfx::Size bounds,
                                   bool preserves3d) {
   layer->SetTransform(transform);