This was caused by https://codereview.chromium.org/2915993004 and reverting that is a potential fix (but it would break some tests that were fixed after that change went in).

https://codereview.chromium.org/2916423002/ is a potential fix as well (although somewhat messy).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c0376a2d193d886e60e2e618be407e4a262446df

commit c0376a2d193d886e60e2e618be407e4a262446df
Author: amp <amp@chromium.org>
Date: Mon Jun 05 22:36:17 2017

[WebVR] Handle slow connecting devices.

A race condition exists when entering WebVR while already in VR (from
VrShell) which slows down devices connecting.  We keep track if we have
seen an immediate handling of the device without a connection (which
signifies that libraries aren't loaded) which allows us to return a 0
count in that case, but return non-zero in the case where a device will
eventually connect.

BUG= 729614 

Review-Url: https://codereview.chromium.org/2916423002
Cr-Commit-Position: refs/heads/master@{#477103}

[modify] https://crrev.com/c0376a2d193d886e60e2e618be407e4a262446df/device/vr/vr_service_impl.cc
[modify] https://crrev.com/c0376a2d193d886e60e2e618be407e4a262446df/device/vr/vr_service_impl.h

Tagging M-60 as the change here will need to be merged back to 60 along with https://codereview.chromium.org/2915993004 to make sure we don't break VrShell to WebVR transitions when we fix the promise resolving for  issue 727969 .

Verified on Canary 61.0.3122.0, requesting merge to 60.

Your change meets the bar and is auto-approved for M60. Please go ahead and merge the CL to branch 3112 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), josafat@(ChromeOS), bustamante@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d15601fcab3d91e87952272473056bfc82f8f141

commit d15601fcab3d91e87952272473056bfc82f8f141
Author: amp <amp@chromium.org>
Date: Tue Jun 06 16:46:23 2017

[WebVR] Handle slow connecting devices.

A race condition exists when entering WebVR while already in VR (from
VrShell) which slows down devices connecting.  We keep track if we have
seen an immediate handling of the device without a connection (which
signifies that libraries aren't loaded) which allows us to return a 0
count in that case, but return non-zero in the case where a device will
eventually connect.

BUG= 729614 
NOTRY=true
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2916423002
Cr-Original-Commit-Position: refs/heads/master@{#477103}
Review-Url: https://codereview.chromium.org/2923823002
Cr-Commit-Position: refs/branch-heads/3112@{#186}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}

[modify] https://crrev.com/d15601fcab3d91e87952272473056bfc82f8f141/device/vr/vr_service_impl.cc
[modify] https://crrev.com/d15601fcab3d91e87952272473056bfc82f8f141/device/vr/vr_service_impl.h