The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/13727a80d7e9fbcdb2631f4066c338c9e55bc288

commit 13727a80d7e9fbcdb2631f4066c338c9e55bc288
Author: Amirhossein Simjour <asimjour@chromium.org>
Date: Thu Feb 08 19:45:51 2018

VR: Close button is added to dialogs in VR

Close button is added to hosted dialogs in VR. This button will
close the quad, moreover it will tell the VrModalPresenter to
dismiss the dialog.

BUG= 809217 

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: If891bad65445002a4a09891a405c61321b5c20d1
Reviewed-on: https://chromium-review.googlesource.com/902885
Commit-Queue: Amirhossein Simjour <asimjour@chromium.org>
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535476}
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrModalPresenter.java
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/android/vr_shell/vr_gl_thread.cc
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/android/vr_shell/vr_gl_thread.h
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/android/vr_shell/vr_shell.cc
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/android/vr_shell/vr_shell.h
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/elements/ui_element_name.cc
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/elements/ui_element_name.h
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/test/mock_ui_browser_interface.h
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/testapp/vr_test_context.cc
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/testapp/vr_test_context.h
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/ui_browser_interface.h
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/ui_scene_constants.h
[modify] https://crrev.com/13727a80d7e9fbcdb2631f4066c338c9e55bc288/chrome/browser/vr/ui_scene_creator.cc

The current behavior has changed such that there is no x on the dialog, clicking outside the dialog causes it to close.  Test have been updated to reflect the new closing behavior.