Attempting to reland the Overview Button Change.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 2334fcfc85d918e71d989e53e40424f26c936011..c67f2da56278d86b76a88f4fd51a6b05fbcd3866 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -299,6 +299,13 @@ class ASH_EXPORT Shell
   // to their final position).
   void OnOverviewModeEnding();
 
+  // 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();
+
   // Initializes |shelf_|.  Does nothing if it's already initialized.
   void CreateShelf();