Note that we also have  issue 725265  for getting rid of AreCrossProcessFramesPossible.  It seems that Ken's latest attempt to re-enable AreCrossProcessFramesPossible on Android is sticking so far after Charlie's --single-process fix (see issues 688617 and 737264), which is great.  Given that, it seems we should now make LayoutTestContentClient::IsSupplementarySiteIsolationModeEnabled always return true as well.

Thanks for pointing out  issue 725265 .  I guess in this case, let's narrow down this bug to just LayoutTestContentClient::IsSupplementarySiteIsolationModeEnabled.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/71b46fc6d0a7385352aa928447c86e698d505460

commit 71b46fc6d0a7385352aa928447c86e698d505460
Author: Lukasz Anforowicz <lukasza@chromium.org>
Date: Tue Jul 18 16:39:13 2017

Enable *.oopif.test for all layout test platforms.

r485361 has made AreCrossProcessFramesPossible return true on all
platforms, including Android.  This CL makes an equivalent change for
layout tests - after this CL all platforms will return |true| from
LayoutTestContentClient::IsSupplementarySiteIsolationModeEnabled.  This
will mean that URLs matching the *oopif.test pattern will be caught by
LayoutTestContentBrowserClient::DoesSiteRequireDedicatedProcess and
pushed into a separate renderer process.

Bug:  745064 
Change-Id: I1311c9e89b1fe45d30575ef923e3b78a097a9dbf
Reviewed-on: https://chromium-review.googlesource.com/574970
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Lukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487498}
[modify] https://crrev.com/71b46fc6d0a7385352aa928447c86e698d505460/content/shell/common/layout_test/layout_test_content_client.cc