Move LayerSorter to exist locally only in layer_tree_host_common

cc/occlusion_tracker_unittest.cc

Index: cc/occlusion_tracker_unittest.cc
diff --git a/cc/occlusion_tracker_unittest.cc b/cc/occlusion_tracker_unittest.cc
index d87b82c1e164650840015c945762f834e97c0567..7c0ceab5fb835ee81ecc2e6f18e67d249e5ea2b8 100644
--- a/cc/occlusion_tracker_unittest.cc
+++ b/cc/occlusion_tracker_unittest.cc
@@ -278,11 +278,10 @@ protected:
     {
         DCHECK(root == m_root.get());
         int dummyMaxTextureSize = 512;
-        LayerSorter layerSorter;
 
         DCHECK(!root->renderSurface());
 
-        LayerTreeHostCommon::calculateDrawProperties(root, root->bounds(), 1, 1, &layerSorter, dummyMaxTextureSize, m_renderSurfaceLayerListImpl);
+        LayerTreeHostCommon::calculateDrawProperties(root, root->bounds(), 1, 1, dummyMaxTextureSize, m_renderSurfaceLayerListImpl);
 
         m_layerIterator = m_layerIteratorBegin = Types::TestLayerIterator::begin(&m_renderSurfaceLayerListImpl);
     }