The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2743e5e5c66d99c241d8044c2478335d26eaaa85

commit 2743e5e5c66d99c241d8044c2478335d26eaaa85
Author: Michael Thiessen <mthiesse@chromium.org>
Date: Thu Feb 22 00:07:32 2018

VR: Show DOFF before intenting out to other Activities when in VR.

Intercepts attempts to start Activities through ChromeActivity and
the Application Context, and shows the DOFF (device off) flow before
starting the requested Activity.

Note that this won't catch all theoretically possible ways to start
Activities in VR, but if we find things that do start activities
through other contexts (like a broadcast receiver?) while in VR, we
have an easy way to fix them.

Bug:  809204 
Change-Id: If29f7bf49ba7261bf8f507fcc9766ee3b610fa29
Reviewed-on: https://chromium-review.googlesource.com/922988
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#538265}
[modify] https://crrev.com/2743e5e5c66d99c241d8044c2478335d26eaaa85/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
[modify] https://crrev.com/2743e5e5c66d99c241d8044c2478335d26eaaa85/chrome/android/java/src/org/chromium/chrome/browser/ChromeApplication.java
[delete] https://crrev.com/f225c329ff85637d6bfdb12df6c16aec13b74595/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrExternalNavigationDelegate.java
[modify] https://crrev.com/2743e5e5c66d99c241d8044c2478335d26eaaa85/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
[modify] https://crrev.com/2743e5e5c66d99c241d8044c2478335d26eaaa85/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
[modify] https://crrev.com/2743e5e5c66d99c241d8044c2478335d26eaaa85/chrome/android/java_sources.gni
[modify] https://crrev.com/2743e5e5c66d99c241d8044c2478335d26eaaa85/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/VrShellTransitionTest.java
[modify] https://crrev.com/2743e5e5c66d99c241d8044c2478335d26eaaa85/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/mock/MockVrDaydreamApi.java

 Issue 808462  has been merged into this issue.

Verified on 66.0.3359.17
Added test case "Exit VR dialog" to "VR Browsing manual test plan" to cover ensure the dialog looks good.