[Refactor] Cache the views::Widget* that the FrameMaximizeButton acts on

ash/wm/custom_frame_view_ash.cc

Index: ash/wm/custom_frame_view_ash.cc
diff --git a/ash/wm/custom_frame_view_ash.cc b/ash/wm/custom_frame_view_ash.cc
index a4b8efb8ac03e936c11b655f5ba7c2cda3c26afb..a606f01a2f492f21030b3c6b655e66cea10e6a58 100644
--- a/ash/wm/custom_frame_view_ash.cc
+++ b/ash/wm/custom_frame_view_ash.cc
@@ -53,7 +53,7 @@ void CustomFrameViewAsh::Init(views::Widget* frame) {
       frame_->widget_delegate()->CanMaximize() ?
           FrameCaptionButtonContainerView::MINIMIZE_ALLOWED :
           FrameCaptionButtonContainerView::MINIMIZE_DISALLOWED;
-  caption_button_container_ = new FrameCaptionButtonContainerView(this, frame,
+  caption_button_container_ = new FrameCaptionButtonContainerView(frame,
       minimize_allowed);
   AddChildView(caption_button_container_);