Use a DownloadRequestHandle pointer in construction to allow mocking for tests.

content/browser/download/download_request_handle.h

 // Copyright (c) 2011 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_DOWNLOAD_DOWNLOAD_REQUEST_HANDLE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_HANDLE_H_
 #pragma once
 
 #include <string>
 
+#include "base/compiler_specific.h"
 #include "content/common/content_export.h"
 
 class DownloadManager;
 class ResourceDispatcherHost;
 class TabContents;
 
 // A handle used by the download system for operations on the URLRequest
 // or objects conditional on it (e.g. TabContents).
 // This class needs to be copyable, so we can pass it across threads and not
 // worry about lifetime or const-ness.
-class CONTENT_EXPORT DownloadRequestHandle {
+//
+// DownloadRequestHandleInterface is defined for mocking purposes.
+class CONTENT_EXPORT DownloadRequestHandleInterface {
+ public:
+  virtual ~DownloadRequestHandleInterface() {}
+
+  // These functions must be called on the UI thread.
+  virtual TabContents* GetTabContents() const = 0;
+  virtual DownloadManager* GetDownloadManager() const = 0;
+
+  // Pause or resume the matching URL request.
+  virtual void PauseRequest() const = 0;
+  virtual void ResumeRequest() const = 0;
+
+  // Cancel the request.
+  virtual void CancelRequest() const = 0;
+
+  // Describe the object.
+  virtual std::string DebugString() const = 0;
+};
+
+
+class CONTENT_EXPORT DownloadRequestHandle
+    : public DownloadRequestHandleInterface {
  public:
   // Create a null DownloadRequestHandle: getters will return null, and
   // all actions are no-ops.
   // TODO(rdsmith): Ideally, actions would be forbidden rather than
   // no-ops, to confirm that no non-testing code actually uses
   // a null DownloadRequestHandle.  But for now, we need the no-op
   // behavior for unit tests.  Long-term, this should be fixed by
   // allowing mocking of ResourceDispatcherHost in unit tests.
   DownloadRequestHandle();
 
   // Note that |rdh| is required to be non-null.
   DownloadRequestHandle(ResourceDispatcherHost* rdh,
                         int child_id,
                         int render_view_id,
                         int request_id);
 
-  // These functions must be called on the UI thread.
-  TabContents* GetTabContents() const;
-  DownloadManager* GetDownloadManager() const;
-
-  // Pause or resume the matching URL request.
-  void PauseRequest() const;
-  void ResumeRequest() const;
-
-  // Cancel the request
-  void CancelRequest() const;
-
-  std::string DebugString() const;
+  // Implement DownloadRequestHandleInterface interface.
+  virtual TabContents* GetTabContents() const OVERRIDE;
+  virtual DownloadManager* GetDownloadManager() const OVERRIDE;
+  virtual void PauseRequest() const OVERRIDE;
+  virtual void ResumeRequest() const OVERRIDE;
+  virtual void CancelRequest() const OVERRIDE;
+  virtual std::string DebugString() const OVERRIDE;
 
  private:
   // The resource dispatcher host.
   ResourceDispatcherHost* rdh_;
 
   // The ID of the child process that started the download.
   int child_id_;
 
   // The ID of the render view that started the download.
   int render_view_id_;
 
   // The ID associated with the request used for the download.
   int request_id_;
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_HANDLE_H_