Refactor Vr activity into ChromeTabbedActivity.

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
index fea48405089447b4fceb2c5400b5c9e36bf8190d..f5f652256276a9ca4dc370a2d5efad349501d0bc 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
@@ -1624,6 +1624,8 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
             HelpAndFeedback.getInstance(this)
                     .show(this, helpContextId, currentTab.getProfile(), currentTab.getUrl());
             RecordUserAction.record("MobileMenuFeedback");
+        } else if (id == R.id.enter_vr_id) {

[Ted C, 2016/09/01 22:38:37]

move this into ChromeTabbedActivity's menu handling code.  enterVR() should be
just there.

[mthiesse, 2016/09/02 01:05:33]

Done.

+            enterVR();
         } else {
             return false;
         }
@@ -1631,6 +1633,18 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
     }
 
     /**
+     * Enters VR Shell, if derived activity is capable of entering VR.
+     */
+    public void enterVR() {}
+
+    /**
+     * Tests if VR Shell is currently enabled.
+     */
+    public boolean isVrShellEnabled() {

[Ted C, 2016/09/01 22:38:37]

Forgive me for being ignorant, but what is VR Shell as a concept?

Shell in chrome is a somewhat overloaded term to me, but I think of something
that is not fully capable (i.e. content shell where it is just the bare minimum
required stuff to show web content).

Is that what this means here?  Is the goal to replace all of this with a
full[er] VR implementation at some point?

What is the long term vision with this?  Is shell the long term naming for this?
 Just wondering why it's not something like isVrModeCapable/supportsVrMode or
something?

[mthiesse, 2016/09/02 01:05:33]

VR Shell has been a highly-debated term. Shell in this instance has no
conceptual relation to other shells like the content shell, and more refers to
the holding or enclosing of VR content.
https://docs.google.com/document/d/16vHXI5_s-Eqttsa6YKnCf-2Tj0yIOTUay1eNyBPkF...
defines the terms we use to describe various concepts and components.

The reason I use isVrShellEnabled is because the compile-time flag for enabling
VR Shell support is 'ENABLE_VR_SHELL', and this function tests compile-time
support. I'm open to changing it, but we have to be careful to make a
distinction between WebVR support and VR Shell support (WebVR support will be
much broader). Terms like HUD are already taken in VR, Chrome VR is too
confusing and overloaded, and VR Mode is too ambiguous.

+        return false;
+    }
+
+    /**
      * Add a view to the set of views that obscure the content of all tabs for
      * accessibility. As long as this set is nonempty, all tabs should be
      * hidden from the accessibility tree.