CrNet: add pauseable NSURLProtocol and switch to using it

ios/crnet/crnet_environment.mm

 // Copyright 2014 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/crnet/crnet_environment.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/at_exit.h"
 #include "base/command_line.h"
@@ skipping 257 matching lines @@
 
   net::SetURLRequestContextForNSSHttpIO(main_context_.get());
   main_context_getter_ = new CrNetURLRequestContextGetter(
       main_context_.get(), network_io_thread_->message_loop_proxy());
   SetRequestFilterBlock(nil);
   net_log_started_ = false;
 }
 
 void CrNetEnvironment::InstallIntoSessionConfiguration(
     NSURLSessionConfiguration* config) {
-  config.protocolClasses = @[ [CRNHTTPProtocolHandler class] ];
+  config.protocolClasses = @[ [CRNPauseableHTTPProtocolHandler class] ];
 }
 
 CrNetEnvironment::~CrNetEnvironment() {
   net::HTTPProtocolHandlerDelegate::SetInstance(nullptr);
   net::SetURLRequestContextForNSSHttpIO(nullptr);
 }
 
 net::URLRequestContextGetter* CrNetEnvironment::GetMainContextGetter() {
   return main_context_getter_.get();
 }
 
 void CrNetEnvironment::SetHTTPProtocolHandlerRegistered(bool registered) {
   if (registered) {
     // Disable the default cache.
     [NSURLCache setSharedURLCache:nil];
     // Register the chrome http protocol handler to replace the default one.
-    BOOL success = [NSURLProtocol registerClass:[CRNHTTPProtocolHandler class]];
+    BOOL success = [NSURLProtocol registerClass:
+        [CRNPauseableHTTPProtocolHandler class]];
     DCHECK(success);
   } else {
     // Set up an empty default cache, with default size.
     // TODO(droger): If the NSURLCache is to be used, its size should most
     // likely be changed. On an iPod2 with iOS4, the default size is 512k.
     [NSURLCache setSharedURLCache:[[[NSURLCache alloc] init] autorelease]];
-    [NSURLProtocol unregisterClass:[CRNHTTPProtocolHandler class]];
+    [NSURLProtocol unregisterClass:[CRNPauseableHTTPProtocolHandler class]];
   }
 }
 
 void CrNetEnvironment::InitializeOnNetworkThread() {
   DCHECK(base::MessageLoop::current() == network_io_thread_->message_loop());
 
   // Register network clients.
   net::RequestTracker::AddGlobalNetworkClientFactory(
       [[[WebPNetworkClientFactory alloc]
           initWithTaskRunner:file_user_blocking_thread_
@@ skipping 142 matching lines @@
       if (backend)
         backend->DoomAllEntries(client_callback);
   });
   int rc = cache->GetBackend(&backend, doom_callback);
   if (rc != net::ERR_IO_PENDING) {
     // GetBackend doesn't call the callback if it completes synchronously, so
     // call it directly here.
     doom_callback.Run(rc);
   }
 }