sync: Refactor per-datatype throttling

sync/sync.gyp

Index: sync/sync.gyp
diff --git a/sync/sync.gyp b/sync/sync.gyp
index da7dbba00351d65769093e9e6bdeff7293456f30..d1322d64c83f1546e826a90f4ad679c98c414310 100644
--- a/sync/sync.gyp
+++ b/sync/sync.gyp
@@ -87,20 +87,22 @@
         'engine/resolve_conflicts_command.h',
         'engine/store_timestamps_command.cc',
         'engine/store_timestamps_command.h',
+        'engine/sync_engine_event.cc',
+        'engine/sync_engine_event.h',
+        'engine/sync_scheduler.cc',
+        'engine/sync_scheduler.h',
         'engine/syncer.cc',
         'engine/syncer.h',
         'engine/syncer_command.cc',
         'engine/syncer_command.h',
-        'engine/sync_engine_event.cc',
-        'engine/sync_engine_event.h',
         'engine/syncer_proto_util.cc',
         'engine/syncer_proto_util.h',
-        'engine/sync_scheduler.cc',
-        'engine/sync_scheduler.h',
         'engine/syncer_types.h',
         'engine/syncer_util.cc',
         'engine/syncer_util.h',
         'engine/syncproto.h',
+        'engine/throttled_data_type_tracker.cc',
+        'engine/throttled_data_type_tracker.h',
         'engine/traffic_logger.cc',
         'engine/traffic_logger.h',
         'engine/traffic_recorder.cc',
@@ -371,25 +373,25 @@
         'sessions/test_util.h',
         'syncable/syncable_mock.cc',
         'syncable/syncable_mock.h',
-        'test/fake_encryptor.cc',
-        'test/fake_encryptor.h',
-        'test/fake_extensions_activity_monitor.cc',
-        'test/fake_extensions_activity_monitor.h',
-        'test/null_directory_change_delegate.cc',
-        'test/null_directory_change_delegate.h',
-        'test/null_transaction_observer.cc',
-        'test/null_transaction_observer.h',
-        'test/engine/test_directory_setter_upper.cc',
-        'test/engine/test_directory_setter_upper.h',
         'test/engine/fake_model_worker.cc',
         'test/engine/fake_model_worker.h',
         'test/engine/mock_connection_manager.cc',
         'test/engine/mock_connection_manager.h',
         'test/engine/syncer_command_test.cc',
         'test/engine/syncer_command_test.h',
+        'test/engine/test_directory_setter_upper.cc',
+        'test/engine/test_directory_setter_upper.h',
         'test/engine/test_id_factory.h',
         'test/engine/test_syncable_utils.cc',
         'test/engine/test_syncable_utils.h',
+        'test/fake_encryptor.cc',
+        'test/fake_encryptor.h',
+        'test/fake_extensions_activity_monitor.cc',
+        'test/fake_extensions_activity_monitor.h',
+        'test/null_directory_change_delegate.cc',
+        'test/null_directory_change_delegate.h',
+        'test/null_transaction_observer.cc',
+        'test/null_transaction_observer.h',
         'test/sessions/test_scoped_session_event_listener.h',
         'test/test_directory_backing_store.cc',
         'test/test_directory_backing_store.h',
@@ -506,8 +508,8 @@
           'internal_api/public/util/enum_set_unittest.cc',
           'engine/apply_updates_command_unittest.cc',
           'engine/build_commit_command_unittest.cc',
-          'engine/clear_data_command_unittest.cc',
           'engine/cleanup_disabled_types_command_unittest.cc',
+          'engine/clear_data_command_unittest.cc',
           'engine/download_updates_command_unittest.cc',
           'engine/model_changing_syncer_command_unittest.cc',
           'engine/nigori_util_unittest.cc',
@@ -515,10 +517,11 @@
           'engine/process_updates_command_unittest.cc',
           'engine/resolve_conflicts_command_unittest.cc',
           'engine/syncer_proto_util_unittest.cc',
-          'engine/sync_scheduler_unittest.cc',
-          'engine/sync_scheduler_whitebox_unittest.cc',
           'engine/syncer_unittest.cc',
           'engine/syncproto_unittest.cc',
+          'engine/sync_scheduler_unittest.cc',
+          'engine/sync_scheduler_whitebox_unittest.cc',
+          'engine/throttled_data_type_tracker_unittest.cc',
           'engine/traffic_recorder_unittest.cc',
           'engine/verify_updates_command_unittest.cc',
           'js/js_arg_list_unittest.cc',
@@ -529,7 +532,6 @@
           'sessions/ordered_commit_set_unittest.cc',
           'sessions/session_state_unittest.cc',
           'sessions/status_controller_unittest.cc',
-          'sessions/sync_session_context_unittest.cc',
           'sessions/sync_session_unittest.cc',
           'syncable/directory_backing_store_unittest.cc',
           'syncable/model_type_unittest.cc',