Update fullscreen ux, make floor and ceiling visible.

chrome/browser/android/vr_shell/ui_scene_manager.h

Index: chrome/browser/android/vr_shell/ui_scene_manager.h
diff --git a/chrome/browser/android/vr_shell/ui_scene_manager.h b/chrome/browser/android/vr_shell/ui_scene_manager.h
index ef917ad5e75a5ee9047b1b309d50fb326c1c7d46..32ebe685d69c888b7fd6eaed430cf75d1627cee6 100644
--- a/chrome/browser/android/vr_shell/ui_scene_manager.h
+++ b/chrome/browser/android/vr_shell/ui_scene_manager.h
@@ -66,6 +66,9 @@ class UiSceneManager {
   UiElement* permanent_security_warning_ = nullptr;
   UiElement* transient_security_warning_ = nullptr;
   UiElement* main_content_ = nullptr;
+  UiElement* ceiling_ = nullptr;

[cjgrant, 2017/05/18 16:07:16]

It really is looking like scene manager should own elements now that it's
native.  Thinking about this for future cleanup...

[amp, 2017/05/18 16:15:33]

I threw this together to get it working quickly in case branch point came at me
quicker than expected, but I still have it in mind set up enums for each element
(as we discussed for testing) and use those instead of hardcoding in elements in
here.

If I have time I want to finish off the tests with the new enum and then rework
this to use those.

As I'm out tomorrow for our move in KIR (our desktops will be off so I can't
even WFH) time will be a little bit tighter, but maybe still doable before
branch point next Thur.

+  UiElement* floor_ = nullptr;
+  UiElement* floor_grid_ = nullptr;
   UiElement* audio_input_indicator_ = nullptr;
   UiElement* video_input_indicator_ = nullptr;
   UrlBar* url_bar_ = nullptr;