Add Mojo API for Blink hit testing

content/renderer/input/frame_input_handler_impl.cc

Index: content/renderer/input/frame_input_handler_impl.cc
diff --git a/content/renderer/input/frame_input_handler_impl.cc b/content/renderer/input/frame_input_handler_impl.cc
index 79be47153609f975e5d780e26d8180e31d2b3405..7d71ee7964bf1936a26cb9164f6e1a0566d5e95b 100644
--- a/content/renderer/input/frame_input_handler_impl.cc
+++ b/content/renderer/input/frame_input_handler_impl.cc
@@ -54,11 +54,11 @@ void FrameInputHandlerImpl::CreateMojoService(
   new FrameInputHandlerImpl(render_frame, std::move(request));
 }
 
-void FrameInputHandlerImpl::RunOnMainThread(const base::Closure& closure) {
+void FrameInputHandlerImpl::RunOnMainThread(base::OnceClosure closure) {
   if (input_event_queue_) {
-    input_event_queue_->QueueClosure(closure);
+    input_event_queue_->QueueClosure(std::move(closure));
   } else {
-    closure.Run();
+    std::move(closure).Run();
   }
 }
 
@@ -247,6 +247,19 @@ void FrameInputHandlerImpl::SelectAll() {
                              UpdateState::kIsSelectingRange));
 }
 
+void FrameInputHandlerImpl::HitTestFrameAt(const gfx::PointF& point,
+                                           HitTestFrameAtCallback callback) {
+  RunOnMainThread(base::BindOnce(&FrameInputHandlerImpl::HitTestOnMainThread,
+                                 weak_this_, point, std::move(callback)));
+}
+
+void FrameInputHandlerImpl::HitTestOnMainThread(
+    const gfx::PointF& point,
+    HitTestFrameAtCallback callback) {
+  std::move(callback).Run(
+      render_frame_->GetRenderWidget()->HitTestFrameAt(point));
+}
+
 void FrameInputHandlerImpl::CollapseSelection() {
   if (!main_thread_task_runner_->BelongsToCurrentThread()) {
     RunOnMainThread(