Render inband text tracks in the media pipeline

content/renderer/media/texttrack_impl.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 "content/renderer/media/texttrack_impl.h"
 
+#include "base/bind.h"
+#include "base/message_loop/message_loop_proxy.h"
 #include "content/renderer/media/webinbandtexttrack_impl.h"
+#include "media/base/bind_to_loop.h"
 #include "third_party/WebKit/public/web/WebInbandTextTrackClient.h"
 #include "third_party/WebKit/public/web/WebMediaPlayerClient.h"
 
 namespace content {
 
-TextTrackImpl::TextTrackImpl(WebKit::WebMediaPlayerClient* client,
-                             WebInbandTextTrackImpl* text_track)
-    : client_(client), text_track_(text_track) {
+TextTrackImpl::TextTrackImpl(
+    const scoped_refptr<base::MessageLoopProxy>& message_loop,
+    WebKit::WebMediaPlayerClient* client,
+    WebInbandTextTrackImpl* text_track)
+    : message_loop_(message_loop),
+      client_(client),
+      text_track_(text_track) {
   client_->addTextTrack(text_track_.get());
 }
 
 TextTrackImpl::~TextTrackImpl() {
-  if (text_track_->client())
-    client_->removeTextTrack(text_track_.get());
+  message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&TextTrackImpl::OnRemoveTrack,
+                 client_,
+                 text_track_.release()));
 }
 
 void TextTrackImpl::addWebVTTCue(const base::TimeDelta& start,
                                  const base::TimeDelta& end,
                                  const std::string& id,
                                  const std::string& content,
                                  const std::string& settings) {
-  if (WebKit::WebInbandTextTrackClient* client = text_track_->client())
-    client->addWebVTTCue(start.InSecondsF(),
-                         end.InSecondsF(),
-                         WebKit::WebString::fromUTF8(id),
-                         WebKit::WebString::fromUTF8(content),
-                         WebKit::WebString::fromUTF8(settings));
+  if (WebKit::WebInbandTextTrackClient* client = text_track_->client()) {

[acolwell GONE FROM CHROMIUM, 2013/10/08 15:45:24]

I don't think this is safe. I think you have to do the text_track->client() eval
inside OnAddCue() because I think the pointer could get cleared while the task
is in flight. You should be able to simply pass text_track_.get() here since you
know that this task will always run before OnRemoveTrack() task that is posted
later.

[Matthew Heaney (Chromium), 2013/10/13 05:30:17]

Done.

+    message_loop_->PostTask(
+      FROM_HERE,
+      base::Bind(&TextTrackImpl::OnAddCue,
+                 client,
+                 start, end,
+                 id, content, settings));
+  }
+}
+
+void TextTrackImpl::OnAddCue(WebKit::WebInbandTextTrackClient* client,
+                             const base::TimeDelta& start,
+                             const base::TimeDelta& end,
+                             const std::string& id,
+                             const std::string& content,
+                             const std::string& settings) {
+  client->addWebVTTCue(start.InSecondsF(),
+                       end.InSecondsF(),
+                       WebKit::WebString::fromUTF8(id),
+                       WebKit::WebString::fromUTF8(content),
+                       WebKit::WebString::fromUTF8(settings));
+}
+
+void TextTrackImpl::OnRemoveTrack(
+    WebKit::WebMediaPlayerClient* client,
+    WebInbandTextTrackImpl* text_track) {

[acolwell GONE FROM CHROMIUM, 2013/10/08 15:45:24]

You should be able to make text_track a scoped_ptr<WebInbandTextTrackImpl> so
you don't need the one below. You'll have to change the .release() to a .Pass()
above as well to make this work.

[Matthew Heaney (Chromium), 2013/10/13 05:30:17]

I had tried that, but the compiler complains about scoped_ptr not having a copy
ctor.

+  scoped_ptr<WebInbandTextTrackImpl> auto_delete(text_track);
+
+  if (text_track->client())
+    client->removeTextTrack(text_track);
 }
 
 }  // namespace content