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

content/browser/frame_host/render_frame_host_impl.cc

Index: content/browser/frame_host/render_frame_host_impl.cc
diff --git a/content/browser/frame_host/render_frame_host_impl.cc b/content/browser/frame_host/render_frame_host_impl.cc
index 1f11c56e75f519c9c7122a5caf842319156c81f9..eafdedcfb15fcf0e3c0667ff2000ede5c3a6be08 100644
--- a/content/browser/frame_host/render_frame_host_impl.cc
+++ b/content/browser/frame_host/render_frame_host_impl.cc
@@ -2394,6 +2394,10 @@ void RenderFrameHostImpl::SetUpMojoIfNeeded() {
     return;
 
   interface_registry_.reset(new shell::InterfaceRegistry(nullptr));
+  // Even in the case that render process host service registry does not exist,
+  // for example, as to test codes using MockRenderProcessHost,
+  // still create |remote_interfaces| to enable register local implementations.
+  remote_interfaces_.reset(new shell::InterfaceProvider(nullptr));
   if (!GetProcess()->GetServiceRegistry())
     return;