WIP Hittest Component.

components/viz/frame_sinks/gpu_root_compositor_frame_sink.h

Index: components/viz/frame_sinks/gpu_root_compositor_frame_sink.h
diff --git a/components/viz/frame_sinks/gpu_root_compositor_frame_sink.h b/components/viz/frame_sinks/gpu_root_compositor_frame_sink.h
index 18df306f331cde0a18d9b0da4444d9d464d1aa3f..c4cdf994012b1b749f89da137d68c2e9d647714a 100644
--- a/components/viz/frame_sinks/gpu_root_compositor_frame_sink.h
+++ b/components/viz/frame_sinks/gpu_root_compositor_frame_sink.h
@@ -12,6 +12,7 @@
 #include "cc/surfaces/local_surface_id.h"
 #include "cc/surfaces/surface_id.h"
 #include "components/viz/frame_sinks/gpu_compositor_frame_sink_delegate.h"
+#include "components/viz/hit_test/hit_test_aggregator.h"
 #include "mojo/public/cpp/bindings/associated_binding.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
@@ -102,6 +103,8 @@ class GpuRootCompositorFrameSink
       compositor_frame_sink_private_binding_;
   mojo::AssociatedBinding<cc::mojom::DisplayPrivate> display_private_binding_;
 
+  std::unique_ptr<hit_test::HitTestAggregator> hit_test_aggregator_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuRootCompositorFrameSink);
 };