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/574970Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Lukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487498}

content/shell/common/layout_test/layout_test_content_client.cc

@@ -21,11 +21,7 @@ bool LayoutTestContentClient::CanSendWhileSwappedOut(
 }
 
 bool LayoutTestContentClient::IsSupplementarySiteIsolationModeEnabled() {
-#if defined(OS_ANDROID)
-  return false;
-#else
   return true;
-#endif
 }
 
 }  // namespace content