Arrange compositor scrolling into scroll customization format

cc/BUILD.gn

Index: cc/BUILD.gn
diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 450754584b6ecec3189e8fb666fccd48d6f076ac..72bc388783498a3bc56e5f0b5482b15de8cc668c 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn
@@ -108,6 +108,8 @@ component("cc") {
     "input/page_scale_animation.h",
     "input/scroll_elasticity_helper.cc",
     "input/scroll_elasticity_helper.h",
+    "input/scroll_state.cc",
+    "input/scroll_state.h",
     "input/selection.h",
     "input/selection_bound_type.h",
     "input/top_controls_manager.cc",
@@ -720,6 +722,7 @@ test("cc_unittests") {
     "base/tiling_data_unittest.cc",
     "debug/frame_timing_tracker_unittest.cc",
     "debug/micro_benchmark_controller_unittest.cc",
+    "input/scroll_state_unittest.cc",
     "input/top_controls_manager_unittest.cc",
     "layers/delegated_frame_provider_unittest.cc",
     "layers/delegated_frame_resource_collection_unittest.cc",