Seems like this is specific to Android.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/02d8a97db2cf9fdca8042ce72416db6b5fc2abbc

commit 02d8a97db2cf9fdca8042ce72416db6b5fc2abbc
Author: sievers <sievers@chromium.org>
Date: Fri Aug 12 01:06:49 2016

Android: Attach hidden layer for CopyFromCompositingSurface()

When the RenderWidgetHostView becomes invisible we might tear down
the layer, which removes the impl layer from the impl layer,
which will cause the Surface not to be added as a dependant Surface
of the root Surface.

Make sure readbacks actually complete (as long as the display is
drawing) by attaching a hidden layer for the readback Surface.

BUG= 636628 
TBR=dtrainor@chromium.org

Review-Url: https://codereview.chromium.org/2243663002
Cr-Commit-Position: refs/heads/master@{#411502}

[modify] https://crrev.com/02d8a97db2cf9fdca8042ce72416db6b5fc2abbc/content/browser/renderer_host/compositor_impl_android.cc
[modify] https://crrev.com/02d8a97db2cf9fdca8042ce72416db6b5fc2abbc/content/browser/renderer_host/compositor_impl_android.h
[modify] https://crrev.com/02d8a97db2cf9fdca8042ce72416db6b5fc2abbc/content/browser/renderer_host/render_widget_host_view_android.cc
[modify] https://crrev.com/02d8a97db2cf9fdca8042ce72416db6b5fc2abbc/content/browser/renderer_host/render_widget_host_view_android.h
[modify] https://crrev.com/02d8a97db2cf9fdca8042ce72416db6b5fc2abbc/ui/android/window_android_compositor.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9df27b364447148d91e8afe8589ab0914fbb3688

commit 9df27b364447148d91e8afe8589ab0914fbb3688
Author: sievers <sievers@chromium.org>
Date: Fri Aug 12 02:21:37 2016

Android: Don't hold frame lock during readback

The problem with this is that it might keep the browser-side
tiles from ever getting freed if for some reason the copy output
request does not finish. And currently there are no such
guarantees for example if the app goes to the background and we don't
have a context and cannot composite.

Also, it would cause jank since the lock keeps from submitting new
frames from the renderer.

As far as readback requests are concerned, this would not cause
the readback to be dropped even if we destroyed the Surface since
it's garbage-collected and there should still be a GC root through
the parent Surface and the hidden layer we attach until the readback
is completed.

Remove more of this logic and public API in a follow-up.

BUG= 636628 

Review-Url: https://codereview.chromium.org/2241633002
Cr-Commit-Position: refs/heads/master@{#411523}

[modify] https://crrev.com/9df27b364447148d91e8afe8589ab0914fbb3688/content/browser/renderer_host/render_widget_host_view_android.cc

Your change meets the bar and is auto-approved for M53 (branch: 2785)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d6837f6960cc65cdf821f1985f68e01240187724

commit d6837f6960cc65cdf821f1985f68e01240187724
Author: Daniel Sievers <sievers@chromium.org>
Date: Mon Aug 15 18:42:41 2016

Android: Attach hidden layer for CopyFromCompositingSurface()

When the RenderWidgetHostView becomes invisible we might tear down
the layer, which removes the impl layer from the impl layer,
which will cause the Surface not to be added as a dependant Surface
of the root Surface.

Make sure readbacks actually complete (as long as the display is
drawing) by attaching a hidden layer for the readback Surface.

BUG= 636628 , 574537 
TBR=dtrainor@chromium.org

Review-Url: https://codereview.chromium.org/2243663002
Cr-Commit-Position: refs/heads/master@{#411502}
(cherry picked from commit 02d8a97db2cf9fdca8042ce72416db6b5fc2abbc)

Review URL: https://codereview.chromium.org/2241383002 .

Cr-Commit-Position: refs/branch-heads/2785@{#599}
Cr-Branched-From: 68623971be0cfc492a2cb0427d7f478e7b214c24-refs/heads/master@{#403382}

[modify] https://crrev.com/d6837f6960cc65cdf821f1985f68e01240187724/content/browser/renderer_host/compositor_impl_android.cc
[modify] https://crrev.com/d6837f6960cc65cdf821f1985f68e01240187724/content/browser/renderer_host/compositor_impl_android.h
[modify] https://crrev.com/d6837f6960cc65cdf821f1985f68e01240187724/content/browser/renderer_host/render_widget_host_view_android.cc
[modify] https://crrev.com/d6837f6960cc65cdf821f1985f68e01240187724/content/browser/renderer_host/render_widget_host_view_android.h
[modify] https://crrev.com/d6837f6960cc65cdf821f1985f68e01240187724/ui/android/window_android_compositor.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ba6da7852ca0d9ef7708f23a8b7c0fd1f93c2cd8

commit ba6da7852ca0d9ef7708f23a8b7c0fd1f93c2cd8
Author: Daniel Sievers <sievers@chromium.org>
Date: Mon Aug 15 18:49:26 2016

Android: Don't hold frame lock during readback

The problem with this is that it might keep the browser-side
tiles from ever getting freed if for some reason the copy output
request does not finish. And currently there are no such
guarantees for example if the app goes to the background and we don't
have a context and cannot composite.

Also, it would cause jank since the lock keeps from submitting new
frames from the renderer.

As far as readback requests are concerned, this would not cause
the readback to be dropped even if we destroyed the Surface since
it's garbage-collected and there should still be a GC root through
the parent Surface and the hidden layer we attach until the readback
is completed.

Remove more of this logic and public API in a follow-up.

BUG= 636628 

Review-Url: https://codereview.chromium.org/2241633002
Cr-Commit-Position: refs/heads/master@{#411523}
(cherry picked from commit 9df27b364447148d91e8afe8589ab0914fbb3688)

Review URL: https://codereview.chromium.org/2247873002 .

Cr-Commit-Position: refs/branch-heads/2785@{#600}
Cr-Branched-From: 68623971be0cfc492a2cb0427d7f478e7b214c24-refs/heads/master@{#403382}

[modify] https://crrev.com/ba6da7852ca0d9ef7708f23a8b7c0fd1f93c2cd8/content/browser/renderer_host/render_widget_host_view_android.cc