[android_webview] Fix UAF in request interception code.

android_webview/browser/net/android_stream_reader_url_request_job.cc

 // 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.
 
 #include "android_webview/browser/net/android_stream_reader_url_request_job.h"
 
 #include <string>
 
 #include "android_webview/browser/input_stream.h"
 #include "android_webview/browser/net/input_stream_reader.h"
@@ skipping 111 matching lines @@
 
 } // namespace
 
 void AndroidStreamReaderURLRequestJob::Start() {
   DCHECK(thread_checker_.CalledOnValidThread());
   // Start reading asynchronously so that all error reporting and data
   // callbacks happen as they would for network requests.
   SetStatus(net::URLRequestStatus(net::URLRequestStatus::IO_PENDING,
                                   net::ERR_IO_PENDING));
 
+  delegate_->OnStart();
+
   // This could be done in the InputStreamReader but would force more
   // complex synchronization in the delegate.
   GetWorkerThreadRunner()->PostTask(
       FROM_HERE,
       base::Bind(
           &OpenInputStreamOnWorkerThread,
           base::MessageLoop::current()->message_loop_proxy(),
           // This is intentional - the job could be deleted while the callback
           // is executing on the background thread.
           // The delegate will be "returned" to the job once the InputStream
@@ skipping 211 matching lines @@
       } else {
         // We don't support multiple range requests in one single URL request,
         // because we need to do multipart encoding here.
         NotifyDone(net::URLRequestStatus(
             net::URLRequestStatus::FAILED,
             net::ERR_REQUEST_RANGE_NOT_SATISFIABLE));
       }
     }
   }
 }