Revert of Ensure BrowserThread::CurrentlyOn is correct through MessageLoop teardown

extensions/browser/extension_function.cc

 // Copyright 2013 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 "extensions/browser/extension_function.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 460 matching lines @@
       delegate_(nullptr) {}
 
 UIThreadExtensionFunction::~UIThreadExtensionFunction() {
   if (dispatcher() && render_frame_host())
     dispatcher()->OnExtensionFunctionCompleted(extension());
   // The extension function should always respond to avoid leaks in the
   // renderer, dangling callbacks, etc. The exception is if the system is
   // shutting down.
   // TODO(devlin): Duplicate this check in IOThreadExtensionFunction. It's
   // tricky because checking IsShuttingDown has to be called from the UI thread.
-  extensions::ExtensionsBrowserClient* browser_client =
-      extensions::ExtensionsBrowserClient::Get();
-  DCHECK(!browser_client || browser_client->IsShuttingDown() || did_respond_ ||
-         ignore_all_did_respond_for_testing_do_not_use)
+  DCHECK(extensions::ExtensionsBrowserClient::Get()->IsShuttingDown() ||
+         did_respond_ || ignore_all_did_respond_for_testing_do_not_use)
       << name_;
 }
 
 UIThreadExtensionFunction*
 UIThreadExtensionFunction::AsUIThreadExtensionFunction() {
   return this;
 }
 
 bool UIThreadExtensionFunction::PreRunValidation(std::string* error) {
   if (!ExtensionFunction::PreRunValidation(error))
@@ skipping 156 matching lines @@
 ExtensionFunction::ResponseAction SyncIOThreadExtensionFunction::Run() {
   return RespondNow(RunSync() ? ArgumentList(std::move(results_))
                               : Error(error_));
 }
 
 // static
 bool SyncIOThreadExtensionFunction::ValidationFailure(
     SyncIOThreadExtensionFunction* function) {
   return false;
 }