Reland of Add PassPaintVisualRectToCompositor feature flag. (patchset #1 id:1...

Reland of Add PassPaintVisualRectToCompositor feature flag. (patchset #1 id:1 of https://codereview.chromium.org/1424783004/ )

Reason for revert:
Reverting the revert.
It turns out ThreadedChannelTestCommit.RunMultiThread_DirectRenderer is flaky and have flaked before this cl.
Sorry for reverting and reverting the revert.

Original issue's description:
> Revert of Add PassPaintVisualRectToCompositor feature flag. (patchset #3 id:40001 of https://codereview.chromium.org/1410573008/ )
>
> Reason for revert:
> Tentative revert since it seems to break http://build.chromium.org/p/chromium.linux/builders/Android%20Tests%20%28dbg%29/builds/31016.
>
> cc_unittests
>
> ThreadedChannelTestCommit.RunMultiThread_DirectRenderer.
>
> Original issue's description:
> > Add PassPaintVisualRectToCompositor feature flag.
> >
> > BUG=529938
> >
> > Committed: https://crrev.com/e8cc107c99f8dea17c02c677270e4e8af3f943c7
> > Cr-Commit-Position: refs/heads/master@{#357052}
>
> TBR=chrishtr@chromium.org,pdr@chromium.org,vmpstr@chromium.org,wkorman@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=529938
>
> Committed: https://crrev.com/31fc911d634e465b22687e78195a494e5e62225c
> Cr-Commit-Position: refs/heads/master@{#357072}

TBR=chrishtr@chromium.org,pdr@chromium.org,vmpstr@chromium.org,wkorman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=529938

Review URL: https://codereview.chromium.org/1421873004

Cr-Commit-Position: refs/heads/master@{#357078}

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

@@ -119,6 +119,7 @@ OrientationEvent
 ForceOverlayFullscreenVideo
 OverlayScrollbars
 PagePopup status=stable
+PassPaintVisualRectToCompositor
 PathOpsSVGClipping status=stable
 PerformanceObserver status=experimental
 Permissions status=stable