Make adding and subtracting gfx:: point types simpler.

ui/gfx/point.cc

Index: ui/gfx/point.cc
diff --git a/ui/gfx/point.cc b/ui/gfx/point.cc
index 322413e9da1d874e42452d4ac3c24a46c7695ed1..c3d1bfe6ec22f1f2843a0668186d8927a6b417e8 100644
--- a/ui/gfx/point.cc
+++ b/ui/gfx/point.cc
@@ -20,6 +20,10 @@ Point::Point() : PointBase<Point, int>(0, 0) {
 Point::Point(int x, int y) : PointBase<Point, int>(x, y) {
 }
 
+Point::Point(const Point& other)
+    : PointBase<Point, int>(other.x(), other.y()) {
+}
+
 #if defined(OS_WIN)
 Point::Point(DWORD point) : PointBase<Point, int>(0, 0){
   POINTS points = MAKEPOINTS(point);