Update BufferedDataSource class documentation.

media/blink/buffered_data_source.cc

 // 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.
 
 #include "media/blink/buffered_data_source.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 84 matching lines @@
       render_task_runner_(task_runner),
       stop_signal_received_(false),
       media_has_played_(false),
       preload_(AUTO),
       bitrate_(0),
       playback_rate_(0.0),
       media_log_(media_log),
       host_(host),
       downloading_cb_(downloading_cb),
       weak_factory_(this) {
   DCHECK(host_);

[DaleCurtis, 2014/11/19 21:14:10]

DCHECK constructed on render_task_runner_ too? 

[no sievers, 2014/11/19 21:16:21]

It's not required in terms of the WeakPtr factory, since the thread binding only
happens when pointers are invalidated or dereferenced.
So in that regard it's ok to create it on another thread as long as you then
only post to it on the main thread.

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

If you want to allow this object to be created on any thread, but then used &
destroyed on the render thread then the class comment needs to say so.

If there's no actual use for that property right now then I'd suggest the more
restrictive create+destroy from render thread requirement be stipulated, and a
DCHECK here.

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

Done.

   DCHECK(!downloading_cb_.is_null());
 }
 
-BufferedDataSource::~BufferedDataSource() {}
+BufferedDataSource::~BufferedDataSource() {
+  DCHECK(render_task_runner_->BelongsToCurrentThread());
+}
 
 // A factory method to create BufferedResourceLoader using the read parameters.
 // This method can be overridden to inject mock BufferedResourceLoader object
 // for testing purpose.
 BufferedResourceLoader* BufferedDataSource::CreateResourceLoader(
     int64 first_byte_position, int64 last_byte_position) {
   DCHECK(render_task_runner_->BelongsToCurrentThread());
 
   BufferedResourceLoader::DeferStrategy strategy = preload_ == METADATA ?
       BufferedResourceLoader::kReadThenDefer :
@@ skipping 407 matching lines @@
   }
 
   // If media is currently playing or the page indicated preload=auto or the
   // the server does not support the byte range request or we do not want to go
   // too far ahead of the read head, use threshold strategy to enable/disable
   // deferring when the buffer is full/depleted.
   loader_->UpdateDeferStrategy(BufferedResourceLoader::kCapacityDefer);
 }
 
 }  // namespace media