[android_webview] Fix UAF in request interception code.

android_webview/browser/net/android_stream_reader_url_request_job_unittest.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/input_stream.h"
 #include "android_webview/browser/net/android_stream_reader_url_request_job.h"
 #include "android_webview/browser/net/aw_url_request_job_factory.h"
 #include "android_webview/browser/net/input_stream_reader.h"
 #include "base/format_macros.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 50 matching lines @@
     return false;
   }
 };
 
 // Required in order to create an instance of AndroidStreamReaderURLRequestJob.
 class StreamReaderDelegate :
     public AndroidStreamReaderURLRequestJob::Delegate {
  public:
   StreamReaderDelegate() {}
 
+  virtual void OnStart() OVERRIDE {}
+
   virtual scoped_ptr<InputStream> OpenInputStream(
       JNIEnv* env,
       const GURL& url) OVERRIDE {
     return make_scoped_ptr<InputStream>(new NotImplInputStream());
   }
 
   virtual void OnInputStreamOpenFailed(net::URLRequest* request,
                                        bool* restart) OVERRIDE {
     *restart = false;
   }
@@ skipping 267 matching lines @@
 
   SetRange(req_.get(), offset, bytes_available);
   req_->Start();
 
   loop.Run();
 
   EXPECT_EQ(0, network_delegate_.completed_requests());
   req_->Cancel();
   EXPECT_EQ(1, network_delegate_.completed_requests());
 }