Make adding and subtracting gfx:: point types simpler.

ui/gfx/size_f.h

Index: ui/gfx/size_f.h
diff --git a/ui/gfx/size_f.h b/ui/gfx/size_f.h
index 591150096ef9a22e5ee174100d8974ed4d67bf28..c377395c57d48d77a1a384db3c807a9eebd767db 100644
--- a/ui/gfx/size_f.h
+++ b/ui/gfx/size_f.h
@@ -8,7 +8,6 @@
 #include <string>
 
 #include "ui/base/ui_export.h"
-#include "ui/gfx/size.h"
 #include "ui/gfx/size_base.h"
 
 namespace gfx {
@@ -20,8 +19,6 @@ class UI_EXPORT SizeF : public SizeBase<SizeF, float> {
   SizeF(float width, float height);
   ~SizeF();
 
-  Size ToSize() const;
-
   std::string ToString() const;
 };