VrShell: Exit fullscreen on app button press.

chrome/browser/android/vr_shell/ui_scene_manager.cc

Index: chrome/browser/android/vr_shell/ui_scene_manager.cc
diff --git a/chrome/browser/android/vr_shell/ui_scene_manager.cc b/chrome/browser/android/vr_shell/ui_scene_manager.cc
index e617824e72653d7d8d1d933655fc7ac35fc2c26a..cbed5626fd00fec52084b839f26ec449575ea0af 100644
--- a/chrome/browser/android/vr_shell/ui_scene_manager.cc
+++ b/chrome/browser/android/vr_shell/ui_scene_manager.cc
@@ -225,6 +225,7 @@ void UiSceneManager::OnAppButtonClicked() {
   content_rendering_enabled_ = !content_rendering_enabled_;
   scene_->SetWebVrRenderingEnabled(content_rendering_enabled_);
   browser_->OnContentPaused(!content_rendering_enabled_);
+  browser_->ExitFullscreen();

[tiborg, 2017/05/10 15:18:50]

What happens if you exit fullscreen on a presenting WebVR page?

[amp, 2017/05/10 15:40:08]

It will check if the web contents are fullscreened and if they are tell it to
exit fullscreen.

I'm pretty sure that when in WebVR the web contents are not fullscreen and so it
should be a no-op, but perhaps we need to be more intelligent about this?

[tiborg, 2017/05/10 15:48:43]

I thought WebVR presentation includes being in fullscreen. But I may be wrong.
If web_contents_->IsFullscreen() returns false for presenting WebVR we are good.

[amp, 2017/05/10 16:15:01]

I just verified with this patch (your comment was a good reminder that I hadn't
checked WebVR).  The app button paused WebVR and pushing it again started it
back up.  If fullscreen had been used then pushing the app button again wouldn't
have worked, so I think we are good. (but let me know if you want me to actually
debug it and check the values).

[tiborg, 2017/05/10 17:01:44]

No, this confirmed this reasonable well. FYI, crrev/2872143002 landed, which
exits WebVR presentation on app button click. I assume you have to rebase on it.
If that works well together (which I think it will) it's all good.

 }
 
 void UiSceneManager::OnAppButtonGesturePerformed(