Remove IsSupplementarySiteIsolationModeEnabled.

It was added in cc0d9147754159827fe40b966cc6db542fc2a571 to
control two things, but after 077f5031e693e9c495203dc5c3360a7f0d3c0c39
it's redundant.

BUG=none

Change-Id: I92d9006226e1f2a0c30ebefd88b893b20bceada3
Reviewed-on: https://chromium-review.googlesource.com/809291
Reviewed-by: Alex Moshchuk <[email protected]>
Reviewed-by: John Abd-El-Malek <[email protected]>
Commit-Queue: Avi Drissman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#523209}
diff --git a/content/browser/site_instance_impl.cc b/content/browser/site_instance_impl.cc
index 61b61fc5..959325f 100644
--- a/content/browser/site_instance_impl.cc
+++ b/content/browser/site_instance_impl.cc
@@ -463,8 +463,7 @@
   // Let the content embedder enable site isolation for specific URLs. Use the
   // canonical site url for this check, so that schemes with nested origins
   // (blob and filesystem) work properly.
-  if (GetContentClient()->IsSupplementarySiteIsolationModeEnabled() &&
-      GetContentClient()->browser()->DoesSiteRequireDedicatedProcess(
+  if (GetContentClient()->browser()->DoesSiteRequireDedicatedProcess(
           browser_context, site_url)) {
     return true;
   }