[Autofill] Migrate ContentAutofillDriver<-->AutofillAgent IPCs to mojo.

content/public/test/mock_render_process_host.cc

Index: content/public/test/mock_render_process_host.cc
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index 5924b5170b3d1df51b16192594dc451f09b81836..8c955eefe17915cb4bbaacfdd096f0d356c899c6 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -104,6 +104,7 @@ void MockRenderProcessHost::EnableSendQueue() {
 
 bool MockRenderProcessHost::Init() {
   has_connection_ = true;
+  remote_interfaces_.reset(new shell::InterfaceProvider);

[sky, 2016/07/22 16:47:48]

This seems reasonable, but we this class also defines SetRemoteInterfaces. Do we
need both?

[leonhsl(Using Gerrit), 2016/07/23 00:41:45]

Good catch~~ I think we can remove SetRemoteInterfaces now, currently its only
user is EmbeddedWorkerTestHelper, which can instead use this empty
InterfaceProvider we initialized here. And I don't think the initial
InterfaceProvider instance needs to be replaced with new one in normal
scenarios. So let's remove SetRemoteInterfaces. 
WDYT? Thanks.

[leonhsl(Using Gerrit), 2016/07/25 06:58:18]

Sorry I had some misunderstanding about MockRenderProcessHost's usage. "I don't
think the initial InterfaceProvider instance needs to be replaced with new one
in normal scenarios." is not true.  In case of EmbeddedWorkerTestHelper, it does
not call MockRenderProcessHost::Init() at all, so no empty InterfaceProvider
gets created there, EmbeddedWorkerTestHelper just creates its own
InterfaceProvider and calls SetRemoteInterfaces() to set into MRPH.

This means that SetRemoteInterfaces() has its own value and we should keep it.
And what we added here is to provide a default value for |remote_interfaces_|.

   return true;
 }