Use ChannelMojo for NaCl PPAPI channels.

components/nacl/loader/nacl_ipc_adapter.h

Index: components/nacl/loader/nacl_ipc_adapter.h
diff --git a/components/nacl/loader/nacl_ipc_adapter.h b/components/nacl/loader/nacl_ipc_adapter.h
index 28e328feda3eea915b6fa1d0721b9e943fccb9f9..b6d07a31c21717f094ed618bd2fce3b0b22f363e 100644
--- a/components/nacl/loader/nacl_ipc_adapter.h
+++ b/components/nacl/loader/nacl_ipc_adapter.h
@@ -31,6 +31,10 @@ struct NaClDesc;
 struct NaClImcTypedMsgHdr;
 struct PP_Size;
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace IPC {
 class Channel;
 struct ChannelHandle;
@@ -105,11 +109,10 @@ class NaClIPCAdapter : public base::RefCountedThreadSafe<NaClIPCAdapter>,
   // |open_resource_cb| may immediately call a OpenResourceReplyCallback
   // function to send a pre-opened resource descriptor to the untrusted side.
   // OpenResourceCallback returns true when OpenResourceReplyCallback is called.
-  NaClIPCAdapter(
-      const IPC::ChannelHandle& handle,
-      base::TaskRunner* runner,
-      ResolveFileTokenCallback resolve_file_token_cb,
-      OpenResourceCallback open_resource_cb);
+  NaClIPCAdapter(const IPC::ChannelHandle& handle,
+                 const scoped_refptr<base::SingleThreadTaskRunner>& runner,

[Mark Seaborn, 2016/10/12 00:57:24]

Can you comment on the reason for this in the commit message, please?  Does Mojo
require a different type of TaskRunner, or is this just a cleanup?

[Sam McNally, 2016/10/12 03:15:32]

ChannelMojo expects to receive the task runner that it's going to used on,
rather than using the thread where Connect() is called (like the other Channel
implementations). The default is to use the current thread, which was incorrect
here, but ignored for other channel types. The task runner parameter for
creating the channel is a SingleThreadTaskRunner, which is the type that's
passed to this constructor anyway.

Changing to a scoped_refptr is just cleanup.

[Mark Seaborn, 2016/10/13 21:27:51]

Ah, that's a nice improvement.  I remember that Chrome IPC's reuse of the thread
that called Connect() has caused some big contortions in the code.

+                 ResolveFileTokenCallback resolve_file_token_cb,
+                 OpenResourceCallback open_resource_cb);
 
   // Initializes with a given channel that's already created for testing
   // purposes. This function will take ownership of the given channel.