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 5675aba5d41e0d1de80352007ae649aba787fe42..64d4ed2482731eedef50c9e9d9708c29f2777ef1 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -322,6 +322,21 @@ void LayerTreeHostImpl::scheduleAnimation()
     m_client->setNeedsRedrawOnImplThread();
 }
 
+bool LayerTreeHostImpl::checkTouchEventHandlerRegionHit(const gfx::Point& viewportPoint)
+{
+
+    gfx::PointF deviceViewportPoint = viewportPoint.Scale(m_deviceScaleFactor);

[danakj, 2012/11/13 00:52:48]

And this should be:

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