Reland: Use a shared thread for media operations.

This reduces the number of threads created per media element by one.

BUG=61293
TBR=acolwell, jamesr, jochen

Review URL: https://codereview.chromium.org/15649017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@203429 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 19 insertions, 0 deletions

diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 386e442..b83ec91 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -1329,6 +1329,16 @@ RenderThreadImpl::GetFileThreadMessageLoopProxy() {
   return file_thread_->message_loop_proxy();
 }
 
+scoped_refptr<base::MessageLoopProxy>
+RenderThreadImpl::GetMediaThreadMessageLoopProxy() {
+  DCHECK(message_loop() == MessageLoop::current());
+  if (!media_thread_) {
+    media_thread_.reset(new base::Thread("Media"));
+    media_thread_->Start();
+  }
+  return media_thread_->message_loop_proxy();
+}
+
 void RenderThreadImpl::SetFlingCurveParameters(
     const std::vector<float>& new_touchpad,
     const std::vector<float>& new_touchscreen) {
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index a7d615b..abdc4d6 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -263,6 +263,11 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
   // on the renderer's main thread.
   scoped_refptr<base::MessageLoopProxy> GetFileThreadMessageLoopProxy();
 
+  // Returns a MessageLoopProxy instance corresponding to the message loop
+  // of the thread on which media operations should be run. Must be called
+  // on the renderer's main thread.
+  scoped_refptr<base::MessageLoopProxy> GetMediaThreadMessageLoopProxy();
+
   // Causes the idle handler to skip sending idle notifications
   // on the two next scheduled calls, so idle notifications are
   // not sent for at least one notification delay.
@@ -433,6 +438,9 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
   // May be null if overridden by ContentRendererClient.
   scoped_ptr<base::Thread> compositor_thread_;
 
+  // Thread for running multimedia operations (e.g., video decoding).
+  scoped_ptr<base::Thread> media_thread_;
+
   // Will point to appropriate MessageLoopProxy after initialization,
   // regardless of whether |compositor_thread_| is overriden.
   scoped_refptr<base::MessageLoopProxy> compositor_message_loop_proxy_;
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 2a8fc58..a51c5a2 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -2837,6 +2837,7 @@ WebMediaPlayer* RenderViewImpl::createMediaPlayer(
   }
 
   webkit_media::WebMediaPlayerParams params(
+      RenderThreadImpl::current()->GetMediaThreadMessageLoopProxy(),
       sink, gpu_factories, new RenderMediaLog());
   WebMediaPlayer* media_player =
       GetContentClient()->renderer()->OverrideCreateWebMediaPlayer(