Add ShellAcceleratorController that managers global keyboard accelerators.

ui/aura_shell/desktop_event_filter.h

Index: ui/aura_shell/desktop_event_filter.h
diff --git a/ui/aura_shell/desktop_event_filter.h b/ui/aura_shell/desktop_event_filter.h
index a5cb2c85922840a45406e7c8b3eec583c6766114..bc0cf5974d9f6b05f4375aa98cf6e3772ab69825 100644
--- a/ui/aura_shell/desktop_event_filter.h
+++ b/ui/aura_shell/desktop_event_filter.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "ui/aura/event_filter.h"
 #include "ui/aura_shell/aura_shell_export.h"
@@ -14,6 +15,8 @@
 namespace aura_shell {
 namespace internal {
 
+class GlobalAcceleratorFilter;
+
 // DesktopEventFilter gets all desktop events first and can provide actions to
 // those events. It implements desktop features such as click to activate a
 // window and cursor change when moving mouse.
@@ -56,6 +59,9 @@ class AURA_SHELL_EXPORT DesktopEventFilter : public aura::EventFilter {
   // Additional event filters that pre-handles events.
   ObserverList<aura::EventFilter, true> filters_;
 
+  // An event filter that pre-handles global accelerators.
+  scoped_ptr<GlobalAcceleratorFilter> global_accelerator_filter_;
+
   DISALLOW_COPY_AND_ASSIGN(DesktopEventFilter);
 };