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

webkit/plugins/ppapi/ppb_graphics_2d_impl.cc

Index: webkit/plugins/ppapi/ppb_graphics_2d_impl.cc
diff --git a/webkit/plugins/ppapi/ppb_graphics_2d_impl.cc b/webkit/plugins/ppapi/ppb_graphics_2d_impl.cc
index 0c0e30bad48bb973e6b4ab143fdad939cf07954b..3de90b639a4969e66ef291aa12a2264a187e745f 100644
--- a/webkit/plugins/ppapi/ppb_graphics_2d_impl.cc
+++ b/webkit/plugins/ppapi/ppb_graphics_2d_impl.cc
@@ -563,7 +563,8 @@ void PPB_Graphics2D_Impl::Paint(WebKit::WebCanvas* canvas,
   SkAutoCanvasRestore auto_restore(canvas, true);
   canvas->clipRect(sk_invalidate_rect);
   gfx::Size pixel_image_size(image_data_->width(), image_data_->height());
-  gfx::Size image_size = gfx::ToFlooredSize(pixel_image_size.Scale(scale_));
+  gfx::Size image_size = gfx::ToFlooredSize(
+      gfx::ScaleSize(pixel_image_size, scale_));
 
   PluginInstance* plugin_instance = ResourceHelper::GetPluginInstance(this);
   if (!plugin_instance)