Move the concept of Activation to the Shell.

ui/aura_shell/shell.h

Index: ui/aura_shell/shell.h
===================================================================
--- ui/aura_shell/shell.h	(revision 114022)
+++ ui/aura_shell/shell.h	(working copy)
@@ -32,6 +32,7 @@
 class ShellTooltipManager;
 
 namespace internal {
+class ActivationController;
 class AppList;
 class DragDropController;
 class ShadowController;
@@ -109,6 +110,7 @@
 
   scoped_ptr<internal::AppList> app_list_;
 
+  scoped_ptr<internal::ActivationController> activation_controller_;
   scoped_ptr<internal::DragDropController> drag_drop_controller_;
   scoped_ptr<internal::WorkspaceController> workspace_controller_;
   scoped_ptr<internal::ShadowController> shadow_controller_;