Attempting to reland the Overview Button Change.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index ee56b839348e74fb9cdb1794e0b3427e5908128f..8b931696920110a2ad201b79fdc83e45ef8b3224 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -388,6 +388,14 @@ void Shell::OnOverviewModeEnding() {
   FOR_EACH_OBSERVER(ShellObserver, observers_, OnOverviewModeEnding());
 }
 
+void Shell::OnMaximizeModeStarted() {
+  FOR_EACH_OBSERVER(ShellObserver, observers_, OnMaximizeModeStarted());
+}
+
+void Shell::OnMaximizeModeEnded() {
+  FOR_EACH_OBSERVER(ShellObserver, observers_, OnMaximizeModeEnded());
+}
+
 void Shell::CreateShelf() {
   RootWindowControllerList controllers = GetAllRootWindowControllers();
   for (RootWindowControllerList::iterator iter = controllers.begin();