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

cc/trees/layer_sorter.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_sorter.h"
 
 #include <algorithm>
 #include <deque>
 #include <limits>
 #include <vector>
@@ skipping 11 matching lines @@
 // a value near machine epsilon and then increasing it until the flickering on
 // the test scene went away.
 const float k_layer_epsilon = 1e-4f;
 
 inline static float PerpProduct(gfx::Vector2dF u, gfx::Vector2dF v) {
   return u.x() * v.y() - u.y() * v.x();
 }
 
 // Tests if two edges defined by their endpoints (a,b) and (c,d) intersect.
 // Returns true and the point of intersection if they do and false otherwise.
-static bool EdgeEdgeTest(gfx::PointF a,
-                         gfx::PointF b,
-                         gfx::PointF c,
-                         gfx::PointF d,
+static bool EdgeEdgeTest(const gfx::PointF& a,
+                         const gfx::PointF& b,
+                         const gfx::PointF& c,
+                         const gfx::PointF& d,
                          gfx::PointF* r) {
   gfx::Vector2dF u = b - a;
   gfx::Vector2dF v = d - c;
   gfx::Vector2dF w = a - c;
 
   float denom = PerpProduct(u, v);
 
   // If denom == 0 then the edges are parallel. While they could be overlapping
   // we don't bother to check here as the we'll find their intersections from
   // the corner to quad tests.
@@ skipping 189 matching lines @@
 
   transform_origin = c1;
 }
 
 LayerShape::~LayerShape() {}
 
 // Returns the Z coordinate of a point on the layer that projects
 // to point p which lies on the z = 0 plane. It does it by computing the
 // intersection of a line starting from p along the Z axis and the plane
 // of the layer.
-float LayerShape::LayerZFromProjectedPoint(gfx::PointF p) const {
+float LayerShape::LayerZFromProjectedPoint(const gfx::PointF& p) const {
   gfx::Vector3dF z_axis(0.f, 0.f, 1.f);
   gfx::Vector3dF w = gfx::Point3F(p) - transform_origin;
 
   float d = gfx::DotProduct(layer_normal, z_axis);
   float n = -gfx::DotProduct(layer_normal, w);
 
   // Check if layer is parallel to the z = 0 axis which will make it
   // invisible and hence returning zero is fine.
   if (!d)
     return 0.f;
@@ skipping 204 matching lines @@
     *it = sorted_list[count++]->layer;
 
   DVLOG(2) << "Sorting end ----";
 
   nodes_.clear();
   edges_.clear();
   active_edges_.clear();
 }
 
 }  // namespace cc