Notify SystemURLRequestContextGetter before shutdown on iOS.

ios/chrome/browser/ios_chrome_io_thread.mm

 // Copyright 2015 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 "ios/chrome/browser/ios_chrome_io_thread.h"
 
 #include <stddef.h>
 
 #include <utility>
 #include <vector>
@@ skipping 187 matching lines @@
 
 class SystemURLRequestContextGetter : public net::URLRequestContextGetter {
  public:
   explicit SystemURLRequestContextGetter(IOSChromeIOThread* io_thread);
 
   // Implementation for net::UrlRequestContextGetter.
   net::URLRequestContext* GetURLRequestContext() override;
   scoped_refptr<base::SingleThreadTaskRunner> GetNetworkTaskRunner()
       const override;
 
+  // Tells the getter that the URLRequestContext is about to be shut down.
+  void Shutdown();
+
  protected:
   ~SystemURLRequestContextGetter() override;
 
  private:
-  IOSChromeIOThread* const
-      io_thread_;  // Weak pointer, owned by ApplicationContext.
+  IOSChromeIOThread* io_thread_;  // Weak pointer, owned by ApplicationContext.
   scoped_refptr<base::SingleThreadTaskRunner> network_task_runner_;
 
   base::debug::LeakTracker<SystemURLRequestContextGetter> leak_tracker_;
 };
 
 SystemURLRequestContextGetter::SystemURLRequestContextGetter(
     IOSChromeIOThread* io_thread)
     : io_thread_(io_thread),
       network_task_runner_(
           web::WebThread::GetTaskRunnerForThread(web::WebThread::IO)) {}
 
 SystemURLRequestContextGetter::~SystemURLRequestContextGetter() {}
 
 net::URLRequestContext* SystemURLRequestContextGetter::GetURLRequestContext() {
   DCHECK_CURRENTLY_ON(web::WebThread::IO);
+  if (!io_thread_)
+    return nullptr;
   DCHECK(io_thread_->globals()->system_request_context.get());
 
   return io_thread_->globals()->system_request_context.get();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 SystemURLRequestContextGetter::GetNetworkTaskRunner() const {
   return network_task_runner_;
 }
 
+void SystemURLRequestContextGetter::Shutdown() {
+  DCHECK_CURRENTLY_ON(web::WebThread::IO);
+  io_thread_ = nullptr;
+  NotifyContextShuttingDown();
+}
+
 IOSChromeIOThread::Globals::SystemRequestContextLeakChecker::
     SystemRequestContextLeakChecker(Globals* globals)
     : globals_(globals) {
   DCHECK(globals_);
 }
 
 IOSChromeIOThread::Globals::SystemRequestContextLeakChecker::
     ~SystemRequestContextLeakChecker() {
   if (globals_->system_request_context.get())
     globals_->system_request_context->AssertNoURLRequests();
@@ skipping 167 matching lines @@
   // get it onto the message loop while the IOSChromeIOThread object still
   // exists.  However, the message might not be processed on the UI
   // thread until after IOSChromeIOThread is gone, so use a weak pointer.
   web::WebThread::PostTask(
       web::WebThread::UI, FROM_HERE,
       base::Bind(&IOSChromeIOThread::InitSystemRequestContext,
                  weak_factory_.GetWeakPtr()));
 }
 
 void IOSChromeIOThread::CleanUp() {
+  system_url_request_context_getter_->Shutdown();
   system_url_request_context_getter_ = nullptr;
 
   // Release objects that the net::URLRequestContext could have been pointing
   // to.
 
   // Shutdown the HistogramWatcher on the IO thread.
   net::NetworkChangeNotifier::ShutdownHistogramWatcher();
 
   // This must be reset before the ChromeNetLog is destroyed.
   network_change_observer_.reset();
@@ skipping 123 matching lines @@
 
   globals->system_http_network_session.reset(
       new net::HttpNetworkSession(system_params));
   globals->system_http_transaction_factory.reset(
       new net::HttpNetworkLayer(globals->system_http_network_session.get()));
   context->set_http_transaction_factory(
       globals->system_http_transaction_factory.get());
 
   return context;
 }