Add Mojo API for Blink hit testing

third_party/WebKit/Source/web/WebViewImpl.cpp

Index: third_party/WebKit/Source/web/WebViewImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebViewImpl.cpp b/third_party/WebKit/Source/web/WebViewImpl.cpp
index 6cde5a4680945779ea86da6e77b4405b1cd34343..3ec3ccc32505785f99540b27d2406cfc1f92ce2c 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.cpp
+++ b/third_party/WebKit/Source/web/WebViewImpl.cpp
@@ -2139,6 +2139,22 @@ bool WebViewImpl::HasVerticalScrollbar() {
 
 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();