Update BufferedDataSource class documentation.

media/blink/buffered_data_source.h

 // Copyright 2013 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 MEDIA_BLINK_BUFFERED_DATA_SOURCE_H_
 #define MEDIA_BLINK_BUFFERED_DATA_SOURCE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 24 matching lines @@
   // pull-based.  http://crbug.com/131444
   virtual void AddBufferedByteRange(int64 start, int64 end) = 0;
 
  protected:
   virtual ~BufferedDataSourceHost() {}
 };
 
 // A data source capable of loading URLs and buffering the data using an
 // in-memory sliding window.
 //
-// BufferedDataSource must be created and initialized on the render thread
-// before being passed to other threads. It may be deleted on any thread.
+// BufferedDataSource is accessed from multiple threads, and it exposes WeakPtrs
+// for posting methods to be run on the main thread. It must therefore also be
+// deleted on the main thread.

[Wez, 2014/11/19 21:38:55]

It doesn't look like it actually exposes WeakPtrs; they seem to be an internal
implementation detail, in which case I'd suggest simply stating that this class
is designed to be created and destroyed from the render thread, although it may
be accessed by other threads while alive.

How are you making sure that the accesses from other threads are synchronized
with this object's teardown, though?

e.g. how do you know that SetBitrate or Stop won't be called on one thread while
this object is being torn down, or after it has been torn down, on the render
thread?

[no sievers, 2014/11/19 21:42:48]

Done.

 class MEDIA_EXPORT BufferedDataSource : public DataSource {
  public:
   // Used to specify video preload states. They are "hints" to the browser about
   // how aggressively the browser should load and buffer data.
   // Please see the HTML5 spec for the descriptions of these values:
   // http://www.w3.org/TR/html5/video.html#attr-media-preload
   //
   // Enum values must match the values in blink::WebMediaPlayer::Preload and
   // there will be assertions at compile time if they do not match.
   enum Preload {
@@ skipping 177 matching lines @@
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<BufferedDataSource> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BufferedDataSource);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_BUFFERED_DATA_SOURCE_H_