mash shelf: Don't create shelf DimmerView in ShelfWidget on mus

ash/shelf/dimmer_view.cc

Index: ash/shelf/dimmer_view.cc
diff --git a/ash/shelf/dimmer_view.cc b/ash/shelf/dimmer_view.cc
index de49e040971486b89671a4b2f1362aaeeee6eac4..83aee9c164437c11dba416afbc35bb3a05855332 100644
--- a/ash/shelf/dimmer_view.cc
+++ b/ash/shelf/dimmer_view.cc
@@ -62,14 +62,6 @@ void DimmerView::SetHovered(bool hovered) {
                                              : BACKGROUND_CHANGE_ANIMATE);
 }
 
-void DimmerView::ForceUndimming(bool force) {
-  bool previous = force_hovered_;
-  force_hovered_ = force;
-  // If the forced change does change the result we apply the change.
-  if (is_hovered_ || force_hovered_ != is_hovered_ || previous)
-    SetHovered(is_hovered_);
-}
-
 void DimmerView::OnPaintBackground(gfx::Canvas* canvas) {
   SkPaint paint;
   ui::ResourceBundle* rb = &ui::ResourceBundle::GetSharedInstance();
@@ -103,6 +95,22 @@ void DimmerView::UpdateBackground(BackgroundAnimator* animator, int alpha) {
 
 void DimmerView::BackgroundAnimationEnded(BackgroundAnimator* animator) {}
 
+views::Widget* DimmerView::GetDimmerWidget() {
+  return GetWidget();
+}
+
+void DimmerView::ForceUndimming(bool force) {
+  bool previous = force_hovered_;
+  force_hovered_ = force;
+  // If the forced change does change the result we apply the change.
+  if (is_hovered_ || force_hovered_ != is_hovered_ || previous)
+    SetHovered(is_hovered_);
+}
+
+int DimmerView::GetDimmingAlphaForTest() {
+  return alpha_;
+}
+
 void DimmerView::OnWindowBoundsChanged(WmWindow* window,
                                        const gfx::Rect& old_bounds,
                                        const gfx::Rect& new_bounds) {