Just need to comment here, FindLayersThatNeedUpdate is going to use LayerListIterator after the CL associated with  crbug.com/592440 .

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2411692cd8bd39dc354fe8fef2a0a948a3df19fd

commit 2411692cd8bd39dc354fe8fef2a0a948a3df19fd
Author: jaydasika <jaydasika@chromium.org>
Date: Wed Mar 23 01:56:09 2016

cc : Update render surfaces using LayerListIterator instead of treewalk

This is the update render surfaces treewalk in draw_property_utils.cc
BUG= 594024 
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1823833002

Cr-Commit-Position: refs/heads/master@{#382767}

[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/test/layer_test_common.cc
[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/test/layer_test_common.h
[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/test/layer_tree_host_common_test.cc
[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/trees/damage_tracker_unittest.cc
[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/trees/draw_property_utils.cc
[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/trees/layer_tree_host_common_unittest.cc
[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/trees/layer_tree_impl_unittest.cc
[modify] https://crrev.com/2411692cd8bd39dc354fe8fef2a0a948a3df19fd/cc/trees/occlusion_tracker_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0c2fd47d62aba824e36bc78560f8c9d4288a30dd

commit 0c2fd47d62aba824e36bc78560f8c9d4288a30dd
Author: jaydasika <jaydasika@chromium.org>
Date: Thu Mar 24 01:26:05 2016

cc : Determine if a layer is root by using the value in LayerTreeImpl

This CL also makes ValidateRenderSurfaces in DrawPropertyUtils use
Layer Iterator.

BUG= 594024 , 568794 
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1832663002

Cr-Commit-Position: refs/heads/master@{#383005}

[modify] https://crrev.com/0c2fd47d62aba824e36bc78560f8c9d4288a30dd/cc/trees/draw_property_utils.cc
[modify] https://crrev.com/0c2fd47d62aba824e36bc78560f8c9d4288a30dd/cc/trees/layer_tree_host_common.cc
[modify] https://crrev.com/0c2fd47d62aba824e36bc78560f8c9d4288a30dd/cc/trees/layer_tree_host_common_unittest.cc
[modify] https://crrev.com/0c2fd47d62aba824e36bc78560f8c9d4288a30dd/cc/trees/layer_tree_host_impl.cc
[modify] https://crrev.com/0c2fd47d62aba824e36bc78560f8c9d4288a30dd/cc/trees/layer_tree_impl.cc
[modify] https://crrev.com/0c2fd47d62aba824e36bc78560f8c9d4288a30dd/cc/trees/layer_tree_impl.h
[modify] https://crrev.com/0c2fd47d62aba824e36bc78560f8c9d4288a30dd/cc/trees/occlusion_tracker.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/369c24b2b6b5cd98b2839bf79675b4aae8eda0f5

commit 369c24b2b6b5cd98b2839bf79675b4aae8eda0f5
Author: jaydasika <jaydasika@chromium.org>
Date: Wed Apr 06 23:44:16 2016

cc : Layers with background filters are drawn only if parent is drawn.

Also changes call from parent to IsRootLayer in draw_property_utils.

BUG= 594024 
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1858233004

Cr-Commit-Position: refs/heads/master@{#385578}

[modify] https://crrev.com/369c24b2b6b5cd98b2839bf79675b4aae8eda0f5/cc/trees/draw_property_utils.cc
[modify] https://crrev.com/369c24b2b6b5cd98b2839bf79675b4aae8eda0f5/cc/trees/layer_tree_host_common_unittest.cc
[modify] https://crrev.com/369c24b2b6b5cd98b2839bf79675b4aae8eda0f5/cc/trees/property_tree.cc