[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 fadeeca42041cb03120150ffe39978fa7c35804d..ee28ece633ca3ea5454cf9713b5d80969d0af936 100644
--- a/content/browser/frame_host/render_frame_host_impl.cc
+++ b/content/browser/frame_host/render_frame_host_impl.cc
@@ -2394,8 +2394,14 @@ void RenderFrameHostImpl::SetUpMojoIfNeeded() {
     return;
 
   interface_registry_.reset(new shell::InterfaceRegistry(nullptr));
-  if (!GetProcess()->GetRemoteInterfaces())
+
+  // The RenderProcessHost may not have remote interfaces in some test
+  // environments. In that case we create an empty InterfaceProvider so tests
+  // can register mock implementations.
+  if (!GetProcess()->GetRemoteInterfaces()) {
+    remote_interfaces_.reset(new shell::InterfaceProvider);
     return;
+  }
 
   RegisterMojoInterfaces();
   mojom::FrameFactoryPtr frame_factory;