Add Mojo API for Blink hit testing

third_party/WebKit/Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 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
@@ skipping 105 matching lines @@
 
   void UpdateAllLifecyclePhases() override;
   void Paint(WebCanvas*, const WebRect&) override;
 #if OS(ANDROID)
   void PaintIgnoringCompositing(WebCanvas*, const WebRect&) override;
 #endif
   void LayoutAndPaintAsync(WebLayoutAndPaintAsyncCallback*) override;
   void CompositeAndReadbackAsync(
       WebCompositeAndReadbackAsyncCallback*) override;
   void ThemeChanged() override;
+  WebFrame* HitTestFrameAt(const WebFloatPoint&) override;
   WebInputEventResult HandleInputEvent(const WebCoalescedInputEvent&) override;
   void SetCursorVisibilityState(bool is_visible) override;
   bool HasTouchEventHandlersAt(const WebPoint&) override;
 
   void ApplyViewportDeltas(const WebFloatSize& visual_viewport_delta,
                            const WebFloatSize& layout_viewport_delta,
                            const WebFloatSize& elastic_overscroll_delta,
                            float page_scale_delta,
                            float browser_controls_shown_ratio_delta) override;
   void RecordWheelAndTouchScrollingCount(bool has_scrolled_by_wheel,
@@ skipping 593 matching lines @@
   Persistent<ResizeViewportAnchor> resize_viewport_anchor_;
 };
 
 // We have no ways to check if the specified WebView is an instance of
 // WebViewImpl because WebViewImpl is the only implementation of WebView.
 DEFINE_TYPE_CASTS(WebViewImpl, WebView, webView, true, true);
 
 }  // namespace blink
 
 #endif