Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/loader/resource_handler.h

 // Copyright (c) 2012 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.
 
 // This is the browser side of the resource dispatcher, it receives requests
 // from the RenderProcessHosts, and dispatches them to URLRequests. It then
 // fowards the messages from the URLRequests back to the correct process for
 // handling.
 //
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
@@ skipping 88 matching lines @@
   // Data will be read for the response.  Upon success, this method places the
   // size and address of the buffer where the data is to be written in its
   // out-params.  This call will be followed by either OnReadCompleted (on
   // successful read or EOF) or OnResponseCompleted (on error).  If
   // OnReadCompleted is called, the buffer may be recycled.  Otherwise, it may
   // not be recycled and may potentially outlive the handler.
   //
   // Unlike other methods, may be called synchronously on Resume, for
   // performance reasons.
   //
-  // If the handler returns false, then the request is cancelled.  Otherwise,
-  // once data is available, OnReadCompleted will be called.
-  // TODO(mmenke):  Make this method use a ResourceController, and allow it to
-  // succeed asynchronously.
-  virtual bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
-                          int* buf_size) = 0;
+  // The request will not continue until one of |controller|'s resume or
+  // cancellation methods is invoked.
+  virtual void OnWillRead(scoped_refptr<net::IOBuffer>* buf,
+                          int* buf_size,
+                          std::unique_ptr<ResourceController> controller) = 0;
 
   // Data (*bytes_read bytes) was written into the buffer provided by
   // OnWillRead.  The request will not continue until one of |controller|'s
   // resume or cancellation methods is invoked.  A zero |bytes_read| signals
   // that no further data will be received.
   virtual void OnReadCompleted(
       int bytes_read,
       std::unique_ptr<ResourceController> controller) = 0;
 
   // The response is complete.  The final response status is given.  The request
@@ skipping 51 matching lines @@
   net::URLRequest* request_;
   Delegate* delegate_;
   std::unique_ptr<ResourceController> controller_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourceHandler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_RESOURCE_HANDLER_H_