Don't post tasks from RulesRegistry c-tor

chrome/browser/extensions/api/web_request/web_request_api.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/browser/extensions/api/web_request/web_request_api.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 1943 matching lines @@
           rules_registries_.end()) {
     relevant_registries.push_back(
         std::make_pair(rules_registries_[cross_profile_rules_key].get(), true));
   }
 
   // The following block is experimentally enabled and its impact on load time
   // logged with UMA Extensions.NetworkDelayRegistryLoad. crbug.com/175961
   for (RelevantRegistries::iterator i = relevant_registries.begin();
        i != relevant_registries.end(); ++i) {
     extensions::WebRequestRulesRegistry* rules_registry = i->first;
-    if (!rules_registry->ready().is_signaled()) {
+    const extensions::OneShotEvent* ready = rules_registry->ready();
+    if (ready && !ready->is_signaled()) {
       // The rules registry is still loading. Block this request until it
       // finishes.
-      rules_registry->ready().Post(
+      ready->Post(
           FROM_HERE,
           base::Bind(&ExtensionWebRequestEventRouter::OnRulesRegistryReady,
                      AsWeakPtr(),
                      profile,
                      event_name,
                      request->identifier(),
                      request_stage));
       blocked_requests_[request->identifier()].num_handlers_blocking++;
       blocked_requests_[request->identifier()].request = request;
       blocked_requests_[request->identifier()].is_incognito |=
@@ skipping 393 matching lines @@
       } else if ((*it)->name().find("AdBlock") != std::string::npos) {
         adblock = true;
       } else {
         other = true;
       }
     }
   }
 
   host->Send(new ExtensionMsg_UsingWebRequestAPI(adblock, adblock_plus, other));
 }