Enable Isolate Extensions by default.

chrome/common/extensions/extension_process_policy.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/common/extensions/extension_process_policy.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_util.h"
 #include "chrome/common/extensions/extension_constants.h"
@@ skipping 61 matching lines @@
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kIsolateExtensions) ||
       base::CommandLine::ForCurrentProcess()->HasSwitch(
           ::switches::kSitePerProcess)) {
     return true;
   }
 
   const std::string group_name =
       base::FieldTrialList::FindFullName("SiteIsolationExtensions");
   // Use StartsWith() for more flexibility (e.g. multiple Enabled groups).
-  return base::StartsWith(group_name, "Enabled",
-                          base::CompareCase::INSENSITIVE_ASCII);
+  bool control_group = base::StartsWith(group_name, "Control",
+                                        base::CompareCase::INSENSITIVE_ASCII);
+  bool default_group = base::StartsWith(group_name, "Default",
+                                        base::CompareCase::INSENSITIVE_ASCII);
+  if (control_group || default_group)

[Devlin, 2017/02/27 19:27:22]

It's strange to me that the default_group behavior doesn't match the "default"
behavior - is this intentional?  Do we have a default group with a population? 
If not, I think it'd make more sense to only gate on Control.

[nasko, 2017/02/27 19:35:14]

Yes, naming is hard ... the "default" group should've been called a "remainder"
group, which is the part of the population that wasn't either Control or
Enabled. Default group removed.

+    return false;
+
+  return true;
 }
 
 }  // namespace extensions