Flip extension background page throttling on by default

R=kalman
BUG=424661

Review URL: https://codereview.chromium.org/1106653002

Cr-Commit-Position: refs/heads/master@{#326953}

extensions/browser/extension_host.cc

@@ -153,12 +153,9 @@ void ExtensionHost::CreateRenderViewNow() {
             "464206 ExtensionHost::CreateRenderViewNow2"));
     DCHECK(IsRenderViewLive());
     if (extension_) {
-      std::string group_name = base::FieldTrialList::FindFullName(
-          "ThrottleExtensionBackgroundPages");
-      if ((group_name == "ThrottlePersistent" &&
-           extensions::BackgroundInfo::HasPersistentBackgroundPage(
-               extension_)) ||
-          group_name == "ThrottleAll") {
+      if (extensions::BackgroundInfo::HasPersistentBackgroundPage(extension_) &&
+          base::FieldTrialList::FindFullName(
+              "ThrottleExtensionBackgroundPages") != "Disabled") {
         host_contents_->WasHidden();
       }
     }