Add Mojo API for Blink hit testing

content/renderer/input/frame_input_handler_impl.h

Index: content/renderer/input/frame_input_handler_impl.h
diff --git a/content/renderer/input/frame_input_handler_impl.h b/content/renderer/input/frame_input_handler_impl.h
index 9c756029f039d5a2648c865abe369d5f64710cd3..8eaf6968e2347c4aa2a4a0051df1995c51bf619d 100644
--- a/content/renderer/input/frame_input_handler_impl.h
+++ b/content/renderer/input/frame_input_handler_impl.h
@@ -64,6 +64,8 @@ class FrameInputHandlerImpl : public mojom::FrameInputHandler {
   void ReplaceMisspelling(const base::string16& word) override;
   void Delete() override;
   void SelectAll() override;
+  void HitTestFrameAt(const gfx::PointF& point,
+                      HitTestFrameAtCallback callback) override;
   void CollapseSelection() override;
   void SelectRange(const gfx::Point& base, const gfx::Point& extent) override;
   void AdjustSelectionByCharacterOffset(int32_t start, int32_t end) override;
@@ -87,10 +89,12 @@ class FrameInputHandlerImpl : public mojom::FrameInputHandler {
   FrameInputHandlerImpl(base::WeakPtr<RenderFrameImpl> render_frame,
                         mojom::FrameInputHandlerRequest request);
 
-  void RunOnMainThread(const base::Closure& closure);
+  void RunOnMainThread(base::OnceClosure closure);
   void BindNow(mojom::FrameInputHandlerRequest request);
   void ExecuteCommandOnMainThread(const std::string& command,
                                   UpdateState state);
+  void HitTestOnMainThread(const gfx::PointF&, HitTestFrameAtCallback);
+
   void Release();
 
   mojo::Binding<mojom::FrameInputHandler> binding_;