Make ResourceHandler::OnWillRead able to complete asynchronously.

content/browser/loader/mock_resource_loader.h

 // Copyright 2016 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 CONTENT_BROWSER_LOADER_MOCK_RESOURCE_LOADER_H_
 #define CONTENT_BROWSER_LOADER_MOCK_RESOURCE_LOADER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 85 matching lines @@
 
   ResourceHandler* const resource_handler_;
 
   Status status_ = Status::IDLE;
   int error_code_ = net::OK;
   bool canceled_out_of_band_ = false;
 
   scoped_refptr<net::IOBuffer> io_buffer_;
   int io_buffer_size_ = 0;
 
+  // True if waiting to receive a buffer due to an OnWillRead call. This does
+  // not affect behavior; it's only used for DCHECKing.
+  bool waiting_on_buffer_ = false;
+
   std::unique_ptr<base::RunLoop> canceled_or_idle_run_loop_;
 
   base::WeakPtrFactory<MockResourceLoader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MockResourceLoader);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_TEST_RESOURCE_HANDLER_WRAPPER_H_