Add API for hit testing layer_impl touchEventHandlerRegions from the host

cc/layer_tree_host_impl.cc

 // Copyright 2011 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.
 
 #include "cc/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 307 matching lines @@
 
     m_client->setNeedsRedrawOnImplThread();
     m_client->setNeedsCommitOnImplThread();
 }
 
 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
     // compute all damage tracking before drawing anything, so that we know the root
     // damage rect. The root damage rect is then used to scissor each surface.
 
     for (int surfaceIndex = renderSurfaceLayerList.size() - 1; surfaceIndex >= 0 ; --surfaceIndex) {
         LayerImpl* renderSurfaceLayer = renderSurfaceLayerList[surfaceIndex];
         RenderSurfaceImpl* renderSurface = renderSurfaceLayer->renderSurface();
         DCHECK(renderSurface);
@@ skipping 1150 matching lines @@
     ScrollbarAnimationController* scrollbarController = layer->scrollbarAnimationController();
     double monotonicTime = (time - base::TimeTicks()).InSecondsF();
     if (scrollbarController && scrollbarController->animate(monotonicTime))
         m_client->setNeedsRedrawOnImplThread();
 
     for (size_t i = 0; i < layer->children().size(); ++i)
         animateScrollbarsRecursive(layer->children()[i], time);
 }
 
 }  // namespace cc