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

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 f9ac6bd890e5b5ab7ec4e7d4c880a5c7f4fef84b..89a9998c6ab9cf6b65b34b0c563f57003d241f94 100644
--- a/ui/gfx/size_f.h
+++ b/ui/gfx/size_f.h
@@ -9,6 +9,7 @@
 
 #include "ui/base/ui_export.h"
 #include "ui/gfx/size_base.h"
+#include "ui/gfx/vector2d_f.h"
 
 namespace gfx {
 
@@ -38,6 +39,10 @@ inline bool operator!=(const SizeF& lhs, const SizeF& rhs) {
   return !(lhs == rhs);
 }
 
+inline SizeF SizeOfVector2d(const Vector2dF& v) {
+  return SizeF(std::abs(v.x()), std::abs(v.y()));
+}
+
 #if !defined(COMPILER_MSVC)
 extern template class SizeBase<SizeF, float>;
 #endif