Fix a focus issue for VR headset activation.

The bug here is that we aren't updating whether to listen for headset
activation when focus changes.

BUG=846661

Change-Id: I029099a6de8b8337d51aa210ad58165fbd01a050
Reviewed-on: https://chromium-review.googlesource.com/1074742
Reviewed-by: Bill Orr <billorr@chromium.org>
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Commit-Queue: Bill Orr <billorr@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#562282}(cherry picked from commit 5345e31)
Reviewed-on: https://chromium-review.googlesource.com/1079795
Cr-Commit-Position: refs/branch-heads/3440@{#49}
Cr-Branched-From: 010ddcf-refs/heads/master@{#561733}

chrome/browser/vr/service/vr_display_host.cc

@@ -115,6 +115,7 @@ void VRDisplayHost::SetListeningForActivate(bool listening) {
 
 void VRDisplayHost::SetInFocusedFrame(bool in_focused_frame) {
   in_focused_frame_ = in_focused_frame;
+  browser_device_->UpdateListeningForActivate(this);
   display_->SetInFocusedFrame(in_focused_frame);
 }