Add Mojo API for Blink hit testing

components/viz/host/host_frame_sink_manager.h

Index: components/viz/host/host_frame_sink_manager.h
diff --git a/components/viz/host/host_frame_sink_manager.h b/components/viz/host/host_frame_sink_manager.h
index e9549b9eb880349b6e5546d724d74064edc27873..10f9b4b89c6a1701b4511af69315d1478e218c16 100644
--- a/components/viz/host/host_frame_sink_manager.h
+++ b/components/viz/host/host_frame_sink_manager.h
@@ -84,6 +84,7 @@ class VIZ_HOST_EXPORT HostFrameSinkManager
   // CompositorFrameSinkSupportManager:
   std::unique_ptr<CompositorFrameSinkSupport> CreateCompositorFrameSinkSupport(
       CompositorFrameSinkSupportClient* client,
+      mojom::TargetFrameForInputDelegate*,
       const FrameSinkId& frame_sink_id,
       bool is_root,
       bool handles_frame_sink_id_invalidation,
@@ -120,6 +121,10 @@ class VIZ_HOST_EXPORT HostFrameSinkManager
     // This will be null if using Mojo.
     CompositorFrameSinkSupport* support = nullptr;
 
+    // Hit test interface from the renderer.
+    mojom::TargetFrameForInputDelegate* target_frame_for_input_delegate =
+        nullptr;
+
    private:
     DISALLOW_COPY_AND_ASSIGN(FrameSinkData);
   };