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 73568ffc3980770b8d8d75d02428522e7cf3552d..78d2d95ffc90a5b2f0720e2d5888be8457fcc23d 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -320,6 +320,21 @@ void LayerTreeHostImpl::scheduleAnimation()
     m_client->setNeedsRedrawOnImplThread();
 }
 
+bool LayerTreeHostImpl::checkTouchEventHandlerRegionHit(const gfx::Point& viewportPoint)
+{
+
+    gfx::PointF deviceViewportPoint = viewportPoint.Scale(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