Implement ScreenOrientationDelegate on ChromeOS

ash/wm/maximize_mode/maximize_mode_controller.cc

Index: ash/wm/maximize_mode/maximize_mode_controller.cc
diff --git a/ash/wm/maximize_mode/maximize_mode_controller.cc b/ash/wm/maximize_mode/maximize_mode_controller.cc
index dc78d281d2cb69534b0c687557cf5db7367ef887..cd50dc2e108372419ea832d96f77c90a8e3bc4ef 100644
--- a/ash/wm/maximize_mode/maximize_mode_controller.cc
+++ b/ash/wm/maximize_mode/maximize_mode_controller.cc
@@ -152,6 +152,11 @@ void MaximizeModeController::SetRotationLocked(bool rotation_locked) {
                     OnRotationLockChanged(rotation_locked_));
 }
 
+void MaximizeModeController::LockRotation(gfx::Display::Rotation rotation) {
+  SetRotationLocked(true);
+  SetDisplayRotation(Shell::GetInstance()->display_manager(), rotation);

[flackr, 2014/10/27 15:12:06]

So if multiple consumers try to lock different orientations the last one wins?
Do the earlier ones need to be informed they lost the lock?

[jonross, 2014/10/27 18:18:48]

For the Javascript api, currently when full-screen is toggled the lock is lost.
The consumer at the time will be notified of the loss.

With our restriction to full-screen tabs there is only ever one consumer at a
time.

Any ash-side consumers, they receive notifications via
MaximizeModeController::Observer

[flackr, 2014/10/27 18:45:19]

This does not seem to be the case. I can open
http://blogs.sitepointstatic.com/examples/tech/full-screen/index.html in two
windows, fullscreen one, alt tab, and fullscreen the other.
I'm worried about conflating the user lock with the application locks. For
example what if?

User locks rotation to landscape, then opens a fullscreen app requesting lock to
portrait? Have we forgotten about the user lock at this point? When the app
unlocks will the user lock be lost?

[jonross, 2014/10/27 21:36:01]

Definitely a problem.

So on Chrome OS the active fullscreen tab can be changed without exiting
fullscreen.
The ScreenOrientation api doesn't listen to this, so the apps do not know.
ScreenOrientation accepts one lock per RenderFrameHost, however separate apps
are separate hosts.
Chrome OS currently has a central lock.
No separation for user vs app.
Requests that arrive all have different ids, even from the same given page. So a
page can overwrite its old lock with a new one, yet not reuse the id.

+}
+
 void MaximizeModeController::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }