cc: Add a flag to layers that returns true if the layer is in RSLL.

This patch adds a flag that says whether the layer is currently in RSLL.
Used to remove layers that previously were in RSLL and are no longer
there.

R=enne, danakj

Review URL: https://codereview.chromium.org/265883013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269353 0039d316-1c4b-4281-b951-d872f2087c98

• cc/layers/draw_properties.h[diff]
• cc/layers/layer_impl.cc[diff]
• cc/layers/layer_impl.h[diff]
• cc/trees/layer_tree_host.cc[diff]
• cc/trees/layer_tree_host_common.cc[diff]
• cc/trees/layer_tree_host_common.h[diff]
• cc/trees/layer_tree_host_common_perftest.cc[diff]
• cc/trees/layer_tree_host_common_unittest.cc[diff]
• cc/trees/layer_tree_impl.cc[diff]
• cc/trees/layer_tree_impl.h[diff]