Add Mojo API for Blink hit testing

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
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 bool WebViewImpl::HasVerticalScrollbar() {
   return MainFrameImpl()
       ->GetFrameView()
       ->LayoutViewportScrollableArea()
       ->VerticalScrollbar();
 }
 
 const WebInputEvent* WebViewImpl::current_input_event_ = nullptr;
 
+WebFrame* WebViewImpl::HitTestFrameAt(const WebFloatPoint& point) {
+  if (!MainFrameImpl())
+    return nullptr;
+
+  HitTestResult hit_test_result =
+      MainFrameImpl()->GetFrame()->GetEventHandler().HitTestResultAtPoint(
+          LayoutPoint((FloatPoint)point));
+  Frame* target_frame = nullptr;
+  Node* target_node = hit_test_result.InnerNode();
+  if (target_node->IsFrameOwnerElement())
+    target_frame = ToHTMLFrameOwnerElement(target_node)->ContentFrame();
+  else
+    target_frame = target_node->GetDocument().GetFrame();
+  return WebFrame::FromFrame(target_frame);
+}
+
 WebInputEventResult WebViewImpl::HandleInputEvent(
     const WebCoalescedInputEvent& coalesced_event) {
   const WebInputEvent& input_event = coalesced_event.Event();
   // TODO(dcheng): The fact that this is getting called when there is no local
   // main frame is problematic and probably indicates a bug in the input event
   // routing code.
   if (!MainFrameImpl())
     return WebInputEventResult::kNotHandled;
 
   GetPage()->GetVisualViewport().StartTrackingPinchStats();
@@ skipping 1977 matching lines @@
   if (focused_frame->LocalFrameRoot() != MainFrameImpl()->GetFrame())
     return nullptr;
   return focused_frame;
 }
 
 LocalFrame* WebViewImpl::FocusedLocalFrameAvailableForIme() const {
   return ime_accept_events_ ? FocusedLocalFrameInWidget() : nullptr;
 }
 
 }  // namespace blink