Replace Ash web notification tray view with a button.

ash/system/tray/tray_background_view.cc

Index: ash/system/tray/tray_background_view.cc
diff --git a/ash/system/tray/tray_background_view.cc b/ash/system/tray/tray_background_view.cc
index 2a87185cecc0e9ec55bd017e0b04a824920990c1..8456ddc280ffefa0b536cf0663fa9d3fd37e3194 100644
--- a/ash/system/tray/tray_background_view.cc
+++ b/ash/system/tray/tray_background_view.cc
@@ -152,7 +152,8 @@ void TrayBackgroundView::TrayContainer::UpdateLayout() {
 // TrayBackgroundView
 
 TrayBackgroundView::TrayBackgroundView(
-    internal::StatusAreaWidget* status_area_widget)
+    internal::StatusAreaWidget* status_area_widget,
+    bool set_background)
     : status_area_widget_(status_area_widget),
       tray_container_(NULL),
       shelf_alignment_(SHELF_ALIGNMENT_BOTTOM),
@@ -171,7 +172,7 @@ TrayBackgroundView::TrayBackgroundView(
       internal::BackgroundAnimator::CHANGE_IMMEDIATE);
 
   tray_container_ = new TrayContainer(shelf_alignment_);
-  SetContents(tray_container_);
+  SetContents(tray_container_, set_background);
 }
 
 TrayBackgroundView::~TrayBackgroundView() {
@@ -235,9 +236,12 @@ void TrayBackgroundView::UpdateBackground(int alpha) {
   SchedulePaint();
 }
 
-void TrayBackgroundView::SetContents(views::View* contents) {
-  background_ = new internal::TrayBackground;
-  contents->set_background(background_);
+void TrayBackgroundView::SetContents(views::View* contents,
+                                     bool set_background) {
+  if (set_background) {
+    background_ = new internal::TrayBackground;
+    contents->set_background(background_);
+  }
 
   SetLayoutManager(new views::BoxLayout(views::BoxLayout::kVertical, 0, 0, 0));
   AddChildView(contents);