Move MaximizeModeController into ash/common

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 6676f29fabacfe309cbedc2d859fb5e4b6d4f5a9..16611fee8c1b0ce94b59712c98b2fcece867d91f 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -280,13 +280,6 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   // Called when a casting session is started or stopped.
   void OnCastingSessionStartedOrStopped(bool started);
 
-  // Called after maximize mode has started, windows might still animate though.
-  void OnMaximizeModeStarted();
-
-  // Called after maximize mode has ended, windows might still be returning to
-  // their original position.
-  void OnMaximizeModeEnded();
-
   // Called when a root window is created.
   void OnRootWindowAdded(WmWindow* root_window);