Add API for hit testing layer_impl touchEventHandlerRegions from the host

cc/layer_tree_host_impl.cc

Index: cc/layer_tree_host_impl.cc
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 01afc00f5ce1147c2ee63b3574c2a64fc0d37e54..dc3b49ff0f78f860f6453b0a2e4a90490487eec6 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -325,6 +325,21 @@ void LayerTreeHostImpl::scheduleAnimation()
     m_client->setNeedsRedrawOnImplThread();
 }
 
+bool LayerTreeHostImpl::haveTouchEventHandlersAt(const gfx::Point& viewportPoint)
+{
+
+    gfx::PointF deviceViewportPoint = gfx::ScalePoint(viewportPoint, m_deviceScaleFactor);
+
+    // First find out which layer was hit from the saved list of visible layers
+    // in the most recent frame.
+    LayerImpl* layerImplHitByPointInTouchHandlerRegion = LayerTreeHostCommon::findLayerThatIsHitByPointInTouchHandlerRegion(deviceViewportPoint, m_renderSurfaceLayerList);
+
+    if (layerImplHitByPointInTouchHandlerRegion)
+      return true;
+
+    return false;
+}
+
 void LayerTreeHostImpl::trackDamageForAllSurfaces(LayerImpl* rootDrawLayer, const LayerList& renderSurfaceLayerList)
 {
     // For now, we use damage tracking to compute a global scissor. To do this, we must