Adding support for sidecars to cc::DisplayItemList.

This is in anticipation of Blink storing its display item data inline in the
cc-side DisplayItemList.

BUG=484943
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1154303004

Cr-Commit-Position: refs/heads/master@{#332317}

diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 297004d..66e8050 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn

@@ -293,6 +293,8 @@
     "playback/display_item.h",
     "playback/display_item_list.cc",
     "playback/display_item_list.h",
+    "playback/display_item_list_settings.cc",
+    "playback/display_item_list_settings.h",
     "playback/display_list_raster_source.cc",
     "playback/display_list_raster_source.h",
     "playback/display_list_recording_source.cc",
@@ -774,6 +776,7 @@
     "base/region_unittest.cc",
     "base/rolling_time_delta_history_unittest.cc",
     "base/scoped_ptr_vector_unittest.cc",
+    "base/sidecar_list_container_unittest.cc",
     "base/simple_enclosed_region_unittest.cc",
     "base/tiling_data_unittest.cc",
     "debug/frame_timing_tracker_unittest.cc",