Move MaximizeModeController into ash/common

ash/common/wm_shell.cc

Index: ash/common/wm_shell.cc
diff --git a/ash/common/wm_shell.cc b/ash/common/wm_shell.cc
index 5d607d60ebc7507ac1f777c2ceeb83c592e23d27..99bda5c96f60c5b26e3e26131026ecf744bc0a84 100644
--- a/ash/common/wm_shell.cc
+++ b/ash/common/wm_shell.cc
@@ -31,6 +31,14 @@ WmShell* WmShell::Get() {
   return instance_;
 }
 
+void WmShell::OnMaximizeModeStarted() {
+  FOR_EACH_OBSERVER(ShellObserver, shell_observers_, OnMaximizeModeStarted());
+}
+
+void WmShell::OnMaximizeModeEnded() {
+  FOR_EACH_OBSERVER(ShellObserver, shell_observers_, OnMaximizeModeEnded());
+}
+
 void WmShell::NotifyPinnedStateChanged(WmWindow* pinned_window) {
   FOR_EACH_OBSERVER(ShellObserver, shell_observers_,
                     OnPinnedStateChanged(pinned_window));