ui: Make gfx::Size::Scale() mutate the class. Add gfx::ScaleSize() similar to Rect/Point.

ui/gfx/rect_f.h

Index: ui/gfx/rect_f.h
diff --git a/ui/gfx/rect_f.h b/ui/gfx/rect_f.h
index 759509105338d70501a4bafc3989394b4829704b..2bc367c94e33cd232a7e4ec025e31cf1e8a1f9ae 100644
--- a/ui/gfx/rect_f.h
+++ b/ui/gfx/rect_f.h
@@ -28,7 +28,7 @@ class UI_EXPORT RectF
 
   ~RectF();
 
-  /// Scales the rectangle by |scale|.
+  // Scales the rectangle by |scale|.
   void Scale(float scale) {
     Scale(scale, scale);
   }
@@ -36,7 +36,7 @@ class UI_EXPORT RectF
   void Scale(float x_scale, float y_scale) {
     set_origin(ScalePoint(origin(), x_scale, y_scale));
 
-    SizeF new_size = size().Scale(x_scale, y_scale);
+    SizeF new_size = gfx::ScaleSize(size(), x_scale, y_scale);
     new_size.ClampToNonNegative();
     set_size(new_size);
   }