Reduce the amount of included header files. Vast change like in "Oh God! This...

net/url_request/mime_sniffer_proxy.h

 // Copyright (c) 2006-2008 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.
 //
 // MimeSnifferProxy wraps an URLRequest to use mime_util's MIME
 // sniffer to better report the content's MIME type.
 // It only supports a subset of the URLRequest API, and must be used together
 // with an URLRequest.  Their lifetimes should be the same.
 //
 // To use it, create a normal URLRequest and initialize it appropriately,
 // then insert a MimeSnifferProxy between your object and the URLRequest:
 //   ms_.reset(new MimeSnifferProxy(url_request, this));
 // It then proxies URLRequest delegate callbacks (from URLRequest back into
 // your object) appropriately.
 //
 // For the other direction of calls (from your object to URLRequest), be sure
 // to use two MimeSniffed functions in place of the URLRequest functions:
 // 1) ms_->Read() -- just like URLRequest::Read()
 // 2) ms_->mime_type() -- returns the sniffed mime type of the data;
 //    valid after OnResponseStarted() is called.
 
 #ifndef NET_URL_REQUEST_MIME_SNIFFER_PROXY_H_
 #define NET_URL_REQUEST_MIME_SNIFFER_PROXY_H_
 
-#include "net/base/io_buffer.h"
 #include "net/url_request/url_request.h"
 
+namespace net {
+class IOBuffer;
+}
+
 class MimeSnifferProxy : public URLRequest::Delegate {
  public:
   // The constructor inserts this MimeSnifferProxy in between the URLRequest
   // and the URLRequest::Delegate, so that the URLRequest's delegate callbacks
   // first go through the MimeSnifferProxy.
   MimeSnifferProxy(URLRequest* request, URLRequest::Delegate* delegate);
 
   // URLRequest::Delegate implementation.
   // These first two functions are handled specially:
   virtual void OnResponseStarted(URLRequest* request);
@@ skipping 34 matching lines @@
   // Whether we've encountered an error on our initial Read().
   bool error_;
 
   // A buffer for the first bit of the request.
   scoped_refptr<net::IOBuffer> buf_;
   // The number of bytes we've read into the buffer.
   int bytes_read_;
 };
 
 #endif  // NET_URL_REQUEST_MIME_SNIFFER_PROXY_H_