Add Vector2d classes that represent offsets, instead of using Point.

ui/gfx/point_f.cc

Index: ui/gfx/point_f.cc
diff --git a/ui/gfx/point_f.cc b/ui/gfx/point_f.cc
index 3d814c53fa3c1e97e72594cdee64dea55f2070dd..d22693a0294af9bc937d1b2c6036804f1822e578 100644
--- a/ui/gfx/point_f.cc
+++ b/ui/gfx/point_f.cc
@@ -8,12 +8,12 @@
 
 namespace gfx {
 
-template class PointBase<PointF, float>;
+template class PointBase<PointF, float, Vector2dF>;
 
-PointF::PointF() : PointBase<PointF, float>(0, 0) {
+PointF::PointF() : PointBase<PointF, float, Vector2dF>(0, 0) {
 }
 
-PointF::PointF(float x, float y) : PointBase<PointF, float>(x, y) {
+PointF::PointF(float x, float y) : PointBase<PointF, float, Vector2dF>(x, y) {
 }
 
 PointF::~PointF() {}