The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ee351c1cd2b342cfbb059447fc0a53f14c7beb16

commit ee351c1cd2b342cfbb059447fc0a53f14c7beb16
Author: Michael Thiessen <mthiesse@chromium.org>
Date: Wed Apr 11 16:29:58 2018

VR: Avoid drawing the overlay Texture when it's empty.

The fallback Android UI path incurs a significant overhead cost to our
rendering pipeline when it's active, which used to be 100% of the time.

This CL uses a dummy canvas that extends the Android canvas and throws
an exception every time something is drawn to it to know whether or not
drawing the view tree was a no-op. If not a no-op, it actually draws
the view tree into our texture-backed canvas.

If the canvas is empty, then we can skip compositing it in our VR
rendering pipeline.

Bug:  830930 
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ic1c93eeae67485e4d4f450598d6b9690d60d99ba
Reviewed-on: https://chromium-review.googlesource.com/999802
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Christopher Grant <cjgrant@chromium.org>
Reviewed-by: Yash Malik <ymalik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549907}
[add] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/EmptySniffingVrViewContainer.java
[add] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/NoopCanvas.java
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrViewContainer.java
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/android/java_sources.gni
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/android/vr/vr_gl_thread.cc
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/android/vr/vr_gl_thread.h
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/android/vr/vr_shell.cc
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/android/vr/vr_shell.h
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/browser_ui_interface.h
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/elements/content_element.cc
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/elements/content_element.h
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/model/model.h
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/test/mock_browser_ui_interface.h
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/ui.cc
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/ui.h
[modify] https://crrev.com/ee351c1cd2b342cfbb059447fc0a53f14c7beb16/chrome/browser/vr/ui_scene_creator.cc