Pass pref_task_runner through HttpServerPropertiesManager's cxtor so that tests could inject a Test…

net/http/http_server_properties_manager.h

 // Copyright 2014 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 NET_HTTP_HTTP_SERVER_PROPERTIES_MANAGER_H_
 #define NET_HTTP_HTTP_SERVER_PROPERTIES_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 63 matching lines @@
     virtual void StartListeningForUpdates(const base::Closure& callback) = 0;
     virtual void StopListeningForUpdates() = 0;
   };
 
   // Create an instance of the HttpServerPropertiesManager.
   //
   // Ownership of the PrefDelegate pointer is taken by this class. This is
   // passed as a raw pointer rather than a scoped_refptr currently because
   // the test uses gmock and it doesn't forward move semantics properly.
   //
   // Must be constructed on the Pref thread.

[brettw, 2016/12/13 23:26:13]

Can you add a description here of the two task runners, why you need two, and
what each one will be used for. I actually don't understand myself so I'll
re-review after that. Thanks!

[Zhongyi Shi, 2016/12/14 19:47:24]

Sorry about the confusion. I have updated the CL description, ptal. Hope that
helps reviewing.

[brettw, 2016/12/14 23:16:54]

Thanks for the description update. But I think we need to update this comment as
well. Somebody calling this function isn't going to find this CL description to
see why there are two task runners and what each one should be.

[Zhongyi Shi, 2016/12/14 23:36:58]

Oh, sorry that I miss the comments in the headers files. Updated now. 

   HttpServerPropertiesManager(
       PrefDelegate* pref_delegate,
+      scoped_refptr<base::SingleThreadTaskRunner> pref_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> network_task_runner);
   ~HttpServerPropertiesManager() override;
 
   // Initialize on Network thread.
   void InitializeOnNetworkThread();
 
   // Prepare for shutdown. Must be called on the Pref thread before destruction.
   void ShutdownOnPrefThread();
 
   // Helper function for unit tests to set the version in the dictionary.
@@ skipping 208 matching lines @@
   // Used to get |weak_ptr_| to self on the network thread.
   std::unique_ptr<base::WeakPtrFactory<HttpServerPropertiesManager>>
       network_weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpServerPropertiesManager);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_SERVER_PROPERTIES_MANAGER_H_