[chromecast] Bind and run mojo media services on cma thread.

media/mojo/services/mojo_media_application.cc

Index: media/mojo/services/mojo_media_application.cc
diff --git a/media/mojo/services/mojo_media_application.cc b/media/mojo/services/mojo_media_application.cc
index 8925e9985eb7658b227bea0def5df91504c46dbd..705c58e7d2cdcc46540ed58d132f0f184806cfbb 100644
--- a/media/mojo/services/mojo_media_application.cc
+++ b/media/mojo/services/mojo_media_application.cc
@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "base/bind_helpers.h"
 #include "media/base/media_log.h"
 #include "media/mojo/services/mojo_media_client.h"
 #include "media/mojo/services/service_factory_impl.h"
@@ -40,10 +41,19 @@ bool MojoMediaApplication::AcceptConnection(mojo::Connection* connection) {
 void MojoMediaApplication::Create(
     mojo::Connection* connection,
     mojo::InterfaceRequest<interfaces::ServiceFactory> request) {
-  // The created object is owned by the pipe.
-  new ServiceFactoryImpl(std::move(request), connection->GetRemoteInterfaces(),
-                         media_log_, ref_factory_.CreateRef(),
-                         mojo_media_client_.get());
+  base::SingleThreadTaskRunner* media_task_runner =
+      mojo_media_client_->media_task_runner();
+  if (!media_task_runner || media_task_runner->BelongsToCurrentThread()) {
+    // The created object is owned by the pipe.
+    new ServiceFactoryImpl(std::move(request),
+                           connection->GetRemoteInterfaces(), media_log_,
+                           ref_factory_.CreateRef(), mojo_media_client_.get());
+  } else {
+    media_task_runner->PostTask(
+        FROM_HERE,
+        base::Bind(&MojoMediaApplication::Create, base::Unretained(this),
+                   connection, base::Passed(&request)));

[xhwang, 2016/04/01 20:10:05]

As far as I understand, a new thread will be created for this app. Then we are
running everything on a different thread.

How about running the app directly on an existing thread where you like it to be
run on? I explored this idea a while back. Here's a prototype CL:
https://chromiumcodereview.appspot.com/1414463005/. It worked for me but then I
didn't need it. It may need some more polish I guess.

[alokp, 2016/04/01 20:44:48]

That would work for our use case. In fact it will be better because we avoid an
additional thread. I guess we could add this by plumbing application task runner
to content::StaticLoader?

But again Ken has indicated that content/ usage of mojo shell is being heavily
refactored, so it may be StaticLoader is going away as well and may not be worth
doing at this point?

+  }
 }
 
 }  // namespace media