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 57b9a143f9703e10706b1ec8078a8cbf6d7d226d..8474b136d8fa8c8d74b9b094c6528128450e46b2 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();