Let's try this out in cases where the URL bar sits at bottom (and that section has been opened). This may behave strangely.

@#4, this also affects that use case. Raising the priority.

Everything works perfectly in the chrome home case, we just enter VR on the page you're viewing and the downloads/history views aren't visible.

In the non-chrome-home case it works well enough for now I think. If you click Downloads or History you get taken to a separate Activity for these, and entering VR on these Activities just takes you to Daydream home as they don't support VR. Literally 0 users will encounter this, and this will be resolved with Chrome Home anyways, so let's ignore this one.

I can't reproduce the case where you see 2D UI for a second or two before being taken to DD home.

If you navigate to chrome://history you see the native history page in VR as expected. Input behaves strangely in this case as noted in  issue 696567 , but given that you would have to enter VR on the chrome://history page and you can't navigate to it while in VR, I expect literally 0 users will encounter this, so we should just target M62 for this fix.

I filed  issue 743103  to track the Chrome Home case (what I saw in #5). The behavior is the same when accessing Downloads and History from Chrome Home.

I do not see the 2D UI either in 61.0.3156.4 in the non-Chrome Home case, though I do see it in  issue 743103 .

chrome://history is different from either case as it is a real tab. I encountered additional problems there ( issue 743119 ). I agree that users are unlikely to encounter this.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8731d22cabb427b5fcddedc8a1135f0b3ba3b4ed

commit 8731d22cabb427b5fcddedc8a1135f0b3ba3b4ed
Author: Michael Thiessen <mthiesse@chromium.org>
Date: Fri Feb 02 21:19:20 2018

VR: Open NTP when we enter VR with no tabs.

Bug: 740731
Change-Id: I7183ebf13db7a317947c3c0aa5b40080258dd60a
Reviewed-on: https://chromium-review.googlesource.com/899782
Reviewed-by: Yash Malik <ymalik@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534155}
[modify] https://crrev.com/8731d22cabb427b5fcddedc8a1135f0b3ba3b4ed/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
[modify] https://crrev.com/8731d22cabb427b5fcddedc8a1135f0b3ba3b4ed/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
[modify] https://crrev.com/8731d22cabb427b5fcddedc8a1135f0b3ba3b4ed/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/VrShellTransitionTest.java

I think this fixes all of the cases where we're in ChromeTabbedActivity and fail to enter VR. We don't yet have a solution for other Activities (like the downloads activity) being open when you enter VR.

Added Test case "Enter VR while displaying a native UI page" to "2D UI handling Test Plan" to ensure we are tracking this.  The current behavior of going directly to Daydream still exists for the native UI, specifically History and Download.

Seems a bit jarring that it would take you to DayDream home but if we're on the launcher, also not the end of the world. If we can fit it into MVP, great, but I think it'd be ok to slide

I just don't see a great way to fix this. We'd have to report the History and Downloads Activities as supporting VR and register the NFC handler intents for them.

Doable, but given how ~0 users will encounter this, and how not-that-bad the effects are, I'd put this down to like a P2...

As in, not something on the VRB hotlist, and probably targeting 69 or 70 given how many other more important things there are.