cc: Remove support for disabling non-root render surfaces.

cc/trees/property_tree.cc

Index: cc/trees/property_tree.cc
diff --git a/cc/trees/property_tree.cc b/cc/trees/property_tree.cc
index 9850577ff4ed778e9f6fd3ce8eb87e7cd57ef092..c92be2c207fc13ddbd84ef86abcd66bc8088a2e6 100644
--- a/cc/trees/property_tree.cc
+++ b/cc/trees/property_tree.cc
@@ -1545,7 +1545,6 @@ PropertyTreesCachedData::~PropertyTreesCachedData() {}
 
 PropertyTrees::PropertyTrees()
     : needs_rebuild(true),
-      non_root_surfaces_enabled(true),
       changed(false),
       full_tree_damaged(false),
       sequence_number(0),
@@ -1580,7 +1579,6 @@ bool PropertyTrees::operator==(const PropertyTrees& other) const {
          full_tree_damaged == other.full_tree_damaged &&
          is_main_thread == other.is_main_thread &&
          is_active == other.is_active &&
-         non_root_surfaces_enabled == other.non_root_surfaces_enabled &&
          sequence_number == other.sequence_number;
 }
 
@@ -1601,7 +1599,6 @@ PropertyTrees& PropertyTrees::operator=(const PropertyTrees& from) {
   needs_rebuild = from.needs_rebuild;
   changed = from.changed;
   full_tree_damaged = from.full_tree_damaged;
-  non_root_surfaces_enabled = from.non_root_surfaces_enabled;
   sequence_number = from.sequence_number;
   is_main_thread = from.is_main_thread;
   is_active = from.is_active;
@@ -1636,7 +1633,6 @@ void PropertyTrees::clear() {
   needs_rebuild = true;
   full_tree_damaged = false;
   changed = false;
-  non_root_surfaces_enabled = true;
   sequence_number++;
 
 #if DCHECK_IS_ON()