Make Callback::Reset() return a copy to support use-cases where Run() ends up modifying |*this|.

media/base/filters.h

 // 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.
 
 // Filters are connected in a strongly typed manner, with downstream filters
 // always reading data from upstream filters.  Upstream filters have no clue
 // who is actually reading from them, and return the results via callbacks.
 //
 //                         DemuxerStream(Video) <- VideoDecoder <- VideoRenderer
 // DataSource <- Demuxer <
@@ skipping 32 matching lines @@
 class Decoder;
 class DemuxerStream;
 class Filter;
 class FilterHost;
 
 struct PipelineStatistics;
 
 // Used for completing asynchronous methods.
 typedef base::Callback<void(PipelineStatus)> FilterStatusCB;
 
-// These functions copy |*cb|, call Reset() on |*cb|, and then call Run()
-// on the copy.  This is used in the common case where you need to clear
-// a callback member variable before running the callback.
-MEDIA_EXPORT void ResetAndRunCB(FilterStatusCB* cb, PipelineStatus status);
-MEDIA_EXPORT void ResetAndRunCB(base::Closure* cb);
-
 class MEDIA_EXPORT Filter : public base::RefCountedThreadSafe<Filter> {
  public:
   Filter();
 
   // Sets the private member |host_|. This is the first method called by
   // the FilterHost after a filter is created.  The host holds a strong
   // reference to the filter.  The reference held by the host is guaranteed
   // to be released before the host object is destroyed by the pipeline.
   virtual void set_host(FilterHost* host);
 
@@ skipping 144 matching lines @@
 
   // Resumes playback after underflow occurs.
   // |buffer_more_audio| is set to true if you want to increase the size of the
   // decoded audio buffer.
   virtual void ResumeAfterUnderflow(bool buffer_more_audio) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_FILTERS_H_