cc: Switch ListContainer to use composition instead of inheritance.

cc/base/BUILD.gn

 # Copyright 2015 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.
 
 source_set("base") {
   visibility = [ "//cc" ]
 
   sources = [
     "completion_event.h",
     "delayed_unique_notifier.cc",
     "delayed_unique_notifier.h",
     "histograms.cc",
     "histograms.h",
     "invalidation_region.cc",
     "invalidation_region.h",
-    "list_container.cc",
     "list_container.h",
+    "list_container_helper.cc",
+    "list_container_helper.h",
     "math_util.cc",
     "math_util.h",
     "region.cc",
     "region.h",
     "resource_id.h",
     "rolling_time_delta_history.cc",
     "rolling_time_delta_history.h",
     "scoped_ptr_algorithm.h",
     "scoped_ptr_deque.h",
     "scoped_ptr_vector.h",
@@ skipping 17 matching lines @@
     "//ui/gfx/geometry",
   ]
 
   defines = [ "CC_IMPLEMENTATION=1" ]
 
   if (!is_debug && (is_win || is_android)) {
     configs -= [ "//build/config/compiler:optimize" ]
     configs += [ "//build/config/compiler:optimize_max" ]
   }
 }