CrNet: add pauseable NSURLProtocol and switch to using it

ios/net/crn_http_protocol_handler_pauseable_proxy.h

Index: ios/net/crn_http_protocol_handler_pauseable_proxy.h
diff --git a/ios/net/crn_http_protocol_handler_pauseable_proxy.h b/ios/net/crn_http_protocol_handler_pauseable_proxy.h
new file mode 100644
index 0000000000000000000000000000000000000000..3c0350329484283983ea7bda0098470b9fb0b791
--- /dev/null
+++ b/ios/net/crn_http_protocol_handler_pauseable_proxy.h
@@ -0,0 +1,26 @@
+// 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.
+
+#ifndef IOS_NET_CRN_HTTP_PROTOCOL_HANDLER_PAUSEABLE_PROXY_H_
+#define IOS_NET_CRN_HTTP_PROTOCOL_HANDLER_PAUSEABLE_PROXY_H_
+
+#import <Foundation/Foundation.h>
+
+#import "ios/net/crn_http_protocol_handler_proxy.h"
+#import "ios/net/crn_http_protocol_handler_proxy_with_client_thread.h"
+
+@interface CRNHTTPProtocolHandlerPauseableProxy
+    : CRNHTTPProtocolHandlerProxyWithClientThread
+
+- (instancetype)initWithProtocol:(NSURLProtocol*)protocol
+                    clientThread:(NSThread*)clientThread
+                     runLoopMode:(NSString*)mode;
+
+- (void)pause;
+
+- (void)resume;
+
+@end
+
+#endif  // IOS_NET_CRN_HTTP_PROTOCOL_HANDLER_PAUSEABLE_PROXY_H_