Change Isolate Extensions to be off by default.

chrome/common/extensions/extension_process_policy.cc

Index: chrome/common/extensions/extension_process_policy.cc
diff --git a/chrome/common/extensions/extension_process_policy.cc b/chrome/common/extensions/extension_process_policy.cc
index 0bb15915d62ec6a0ff7215d17537e3d813502aa4..59fb528efd9031584886a596fefe89828bc9aaf7 100644
--- a/chrome/common/extensions/extension_process_policy.cc
+++ b/chrome/common/extensions/extension_process_policy.cc
@@ -8,6 +8,7 @@
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_util.h"
 #include "chrome/common/extensions/extension_constants.h"
+#include "content/public/common/content_switches.h"
 #include "extensions/common/constants.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extension_set.h"
@@ -68,11 +69,18 @@ bool CrossesExtensionProcessBoundary(
 }
 
 bool IsIsolateExtensionsEnabled() {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kIsolateExtensions) ||
+      base::CommandLine::ForCurrentProcess()->HasSwitch(
+          ::switches::kSitePerProcess)) {
+    return true;
+  }
+
   const std::string group_name =
       base::FieldTrialList::FindFullName("SiteIsolationExtensions");
-  bool is_control_group = base::StartsWith(
-      group_name, "Control", base::CompareCase::INSENSITIVE_ASCII);
-  return !is_control_group;
+  // Use StartsWith() for more flexibility (e.g. multiple Enabled groups).
+  return base::StartsWith(group_name, "Enabled",
+                          base::CompareCase::INSENSITIVE_ASCII);
 }
 
 }  // namespace extensions