Add Mojo API for Blink hit testing

content/renderer/render_widget.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_RENDER_WIDGET_H_
 #define CONTENT_RENDERER_RENDER_WIDGET_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 403 matching lines @@
       const blink::WebActiveWheelFlingParameters& params) {}
 
   uint32_t GetContentSourceId();
   void IncrementContentSourceId();
 
   // MainThreadEventQueueClient overrides.
 
   // Requests a BeginMainFrame callback from the compositor.
   void SetNeedsMainFrame() override;
 
+  int HitTestFrameAt(const gfx::PointF& point);
+
   void HandleInputEvent(const blink::WebCoalescedInputEvent& input_event,
                         const ui::LatencyInfo& latency_info,
                         HandledEventCallback callback) override;
 
   scoped_refptr<MainThreadEventQueue> GetInputEventQueue();
 
  protected:
   // Friend RefCounted so that the dtor can be non-public. Using this class
   // without ref-counting is an error.
   friend class base::RefCounted<RenderWidget>;
@@ skipping 464 matching lines @@
   scoped_refptr<MainThreadEventQueue> input_event_queue_;
 
   base::WeakPtrFactory<RenderWidget> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_WIDGET_H_