Refactor PhantomWindowController so that the PhantomWindowController owns the phantom window

ash/wm/caption_buttons/alternate_frame_size_button.h

Index: ash/wm/caption_buttons/alternate_frame_size_button.h
diff --git a/ash/wm/caption_buttons/alternate_frame_size_button.h b/ash/wm/caption_buttons/alternate_frame_size_button.h
index 586eabbeb99ce7b2a4b73b9b475c375e60e14fce..f7a0f7a4766ef3c290b618f4a66793ee9f232bdf 100644
--- a/ash/wm/caption_buttons/alternate_frame_size_button.h
+++ b/ash/wm/caption_buttons/alternate_frame_size_button.h
@@ -18,6 +18,10 @@ class Widget;
 namespace ash {
 class AlternateFrameSizeButtonDelegate;
 
+namespace internal {
+class PhantomWindowController;
+}
+
 // The maximize/restore button when using the alternate button style.
 // When the mouse is pressed over the size button or the size button is touched:
 // - The minimize and close buttons are set to snap left and snap right
@@ -92,6 +96,11 @@ class ASH_EXPORT AlternateFrameSizeButton : public FrameCaptionButton {
   // the size button's default action is run when clicked.
   SnapType snap_type_;
 
+  // Displays a preview of how the window's bounds will change as a result of
+  // snapping the window left or right. The preview is only visible if the snap
+  // left or snap right button is pressed.
+  scoped_ptr<internal::PhantomWindowController> phantom_window_controller_;
+
   DISALLOW_COPY_AND_ASSIGN(AlternateFrameSizeButton);
 };