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

ash/common/system/tray/system_tray_item.h

Index: ash/common/system/tray/system_tray_item.h
diff --git a/ash/common/system/tray/system_tray_item.h b/ash/common/system/tray/system_tray_item.h
index c1e6aaba425844280a9c054f7770a1e762d53782..854bd2342aca980214e68f97285ecf80d60968e0 100644
--- a/ash/common/system/tray/system_tray_item.h
+++ b/ash/common/system/tray/system_tray_item.h
@@ -5,11 +5,17 @@
 #ifndef ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_
 #define ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_
 
+#include <memory>
+
 #include "ash/ash_export.h"
 #include "ash/common/login_status.h"
 #include "ash/public/cpp/shelf_types.h"
 #include "base/macros.h"
 
+namespace base {
+class OneShotTimer;
+}  // namespace base
+
 namespace views {
 class View;
 }
@@ -105,8 +111,9 @@ class ASH_EXPORT SystemTrayItem {
   // currently visible, then making this call would use the existing window to
   // display the detailed item. The detailed item will inherit the bounds of the
   // existing window.
-  // If there is no existing view, then this is equivalent to calling
-  // PopupDetailedView(0, true).
+  //
+  // In Material Design the actual transition is intentionally delayed to allow
+  // the user to perceive the ink drop animation on the clicked target.
   void TransitionDetailedView();
 
   // Pops up the detailed view for this item. An item can request to show its
@@ -142,6 +149,9 @@ class ASH_EXPORT SystemTrayItem {
   void set_restore_focus(bool restore_focus) { restore_focus_ = restore_focus; }
 
  private:
+  // Actually transitions to the detailed view.
+  void DoTransitionToDetailedView();
+
   // Accesses uma_type().
   friend class SystemTrayBubble;
 
@@ -151,6 +161,9 @@ class ASH_EXPORT SystemTrayItem {
   UmaType uma_type_;
   bool restore_focus_;
 
+  // Used to delay the transition to the detailed view.
+  std::unique_ptr<base::OneShotTimer> transition_delay_timer_;
+
   DISALLOW_COPY_AND_ASSIGN(SystemTrayItem);
 };