Allow arc app to lock screen orientation in TouchView/Tablet mode

ash/display/screen_orientation_controller_chromeos.cc

Index: ash/display/screen_orientation_controller_chromeos.cc
diff --git a/ash/display/screen_orientation_controller_chromeos.cc b/ash/display/screen_orientation_controller_chromeos.cc
index 3bbb8c55a912650a275c3d608d10efa390e24daa..285cf5c414c131ee38a16004538d4553f9b93875 100644
--- a/ash/display/screen_orientation_controller_chromeos.cc
+++ b/ash/display/screen_orientation_controller_chromeos.cc
@@ -112,6 +112,15 @@ void ScreenOrientationController::UnlockOrientationForWindow(
   ApplyLockForActiveWindow();
 }
 
+void ScreenOrientationController::UnlockAll() {
+  for (auto pair : locking_windows_)
+    pair.first->RemoveObserver(this);
+  locking_windows_.clear();
+  Shell::GetInstance()->activation_client()->RemoveObserver(this);
+  if (user_rotation_ != current_rotation_)
+    SetDisplayRotation(user_rotation_, display::Display::ROTATION_SOURCE_USER);

[oshima, 2016/06/30 22:59:24]

We're unlocking all, not just arc windows, but I believe this is what we want.

If this works for arc++ enabled devices, I'll merge this to OnMaximizeModeEnded
below.

+}
+
 bool ScreenOrientationController::ScreenOrientationProviderSupported() const {
   return Shell::GetInstance()
              ->maximize_mode_controller()