[ash-md] Added a delay between system menu default/detailed view transitions.

ash/common/system/tray/tray_details_view.h

Index: ash/common/system/tray/tray_details_view.h
diff --git a/ash/common/system/tray/tray_details_view.h b/ash/common/system/tray/tray_details_view.h
index 003233959f2caa962d3e3d15dd1552c6fd800fca..3998d48fb78b6ee5fc994e652e3e1727808e2ef0 100644
--- a/ash/common/system/tray/tray_details_view.h
+++ b/ash/common/system/tray/tray_details_view.h
@@ -5,13 +5,20 @@
 #ifndef ASH_COMMON_SYSTEM_TRAY_TRAY_DETAILS_VIEW_H_
 #define ASH_COMMON_SYSTEM_TRAY_TRAY_DETAILS_VIEW_H_
 
+#include <memory>
+
 #include "ash/ash_export.h"
 #include "ash/common/system/tray/special_popup_row.h"
+#include "ash/common/system/tray/tray_constants.h"
 #include "ash/common/system/tray/view_click_listener.h"
 #include "base/macros.h"
 #include "ui/views/controls/button/button.h"
 #include "ui/views/view.h"
 
+namespace base {
+class OneShotTimer;
+}  // namespace base
+
 namespace views {
 class BoxLayout;
 class CustomButton;
@@ -110,8 +117,14 @@ class ASH_EXPORT TrayDetailsView : public views::View,
   // Transition to default view from details view. If |title_row_| has focus
   // before transition, the default view should focus on the owner of this
   // details view.
+  //
+  // In Material Design the actual transition is intentionally delayed to allow
+  // the user to perceive the ink drop animation on the clicked target.
   void TransitionToDefaultView();
 
+  // Actually transitions to the default view.
+  void DoTransitionToDefaultView();
+
   // Helper function which creates and returns the back button used in the
   // material design top-most header row. The caller assumes ownership of the
   // returned button.
@@ -135,6 +148,9 @@ class ASH_EXPORT TrayDetailsView : public views::View,
   // The back button that appears in the material design title row. Not owned.
   views::Button* back_button_;
 
+  // Used to delay the transition to the default view.
+  std::unique_ptr<base::OneShotTimer> transition_delay_timer_;
+
   DISALLOW_COPY_AND_ASSIGN(TrayDetailsView);
 };