[#5] Pass gfx structs by const ref (gfx::Vector2dF)

cc/base/math_util.h

Index: cc/base/math_util.h
diff --git a/cc/base/math_util.h b/cc/base/math_util.h
index c598fcff47f293750db843fa85a4f74cd1f467a5..6cad1ad1c5a4022bcb6ecb9957adef4fecc93225 100644
--- a/cc/base/math_util.h
+++ b/cc/base/math_util.h
@@ -156,13 +156,13 @@ class CC_EXPORT MathUtil {
 
   // Returns the smallest angle between the given two vectors in degrees.
   // Neither vector is assumed to be normalized.
-  static float SmallestAngleBetweenVectors(gfx::Vector2dF v1,
-                                           gfx::Vector2dF v2);
+  static float SmallestAngleBetweenVectors(const gfx::Vector2dF& v1,
+                                           const gfx::Vector2dF& v2);
 
   // Projects the |source| vector onto |destination|. Neither vector is assumed
   // to be normalized.
-  static gfx::Vector2dF ProjectVector(gfx::Vector2dF source,
-                                      gfx::Vector2dF destination);
+  static gfx::Vector2dF ProjectVector(const gfx::Vector2dF& source,
+                                      const gfx::Vector2dF& destination);
 
   // Conversion to value.
   static scoped_ptr<base::Value> AsValue(gfx::Size s);