chromeos: convert more ash/wm code to aura::Window

ash/frame/caption_buttons/frame_size_button.cc

Index: ash/frame/caption_buttons/frame_size_button.cc
diff --git a/ash/frame/caption_buttons/frame_size_button.cc b/ash/frame/caption_buttons/frame_size_button.cc
index a98ba8cba1204b353af8c9ab595509fd52fcee0c..5da850187d642b32cbe5b435c49ed177c2c89236 100644
--- a/ash/frame/caption_buttons/frame_size_button.cc
+++ b/ash/frame/caption_buttons/frame_size_button.cc
@@ -213,7 +213,8 @@ void FrameSizeButton::UpdateSnapType(const ui::LocatedEvent& event) {
   if (snap_type_ == SNAP_LEFT || snap_type_ == SNAP_RIGHT) {
     aura::Window* window = frame_->GetNativeWindow();
     if (!phantom_window_controller_.get()) {
-      phantom_window_controller_.reset(new PhantomWindowController(window));
+      phantom_window_controller_ =
+          base::MakeUnique<PhantomWindowController>(window);
     }
     gfx::Rect phantom_bounds_in_screen =
         (snap_type_ == SNAP_LEFT)