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);
+  return !base::StartsWith(group_name, "Control",
+                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
 }  // namespace extensions