sync: Introduce classes for per-type counters

sync/sync_internal_api.gypi

Index: sync/sync_internal_api.gypi
diff --git a/sync/sync_internal_api.gypi b/sync/sync_internal_api.gypi
index 2e677fe494669cf3f1413e39893b3bf75b879ff0..2a0c2745a8e2471abe09560ba0eaf64231ce17ad 100644
--- a/sync/sync_internal_api.gypi
+++ b/sync/sync_internal_api.gypi
@@ -95,10 +95,18 @@
     'internal_api/public/non_blocking_type_processor.h',
     'internal_api/public/read_node.h',
     'internal_api/public/read_transaction.h',
+    'internal_api/public/sessions/commit_counters.cc',
+    'internal_api/public/sessions/commit_counters.h',
     'internal_api/public/sessions/model_neutral_state.cc',
     'internal_api/public/sessions/model_neutral_state.h',
+    'internal_api/public/sessions/status_counters.cc',
+    'internal_api/public/sessions/status_counters.h',
     'internal_api/public/sessions/sync_session_snapshot.cc',
     'internal_api/public/sessions/sync_session_snapshot.h',
+    'internal_api/public/sessions/type_debug_info_observer.cc',
+    'internal_api/public/sessions/type_debug_info_observer.h',
+    'internal_api/public/sessions/update_counters.cc',
+    'internal_api/public/sessions/update_counters.h',
     'internal_api/public/sync_core_proxy.h',
     'internal_api/public/sync_encryption_handler.cc',
     'internal_api/public/sync_encryption_handler.h',
@@ -134,10 +142,10 @@
     'internal_api/sync_manager_factory.cc',
     'internal_api/sync_manager_impl.cc',
     'internal_api/sync_manager_impl.h',
-    'internal_api/sync_rollback_manager_base.cc',
-    'internal_api/sync_rollback_manager_base.h',    
     'internal_api/sync_rollback_manager.cc',
-    'internal_api/sync_rollback_manager.h',    
+    'internal_api/sync_rollback_manager.h',
+    'internal_api/sync_rollback_manager_base.cc',
+    'internal_api/sync_rollback_manager_base.h',
     'internal_api/syncapi_internal.cc',
     'internal_api/syncapi_internal.h',
     'internal_api/syncapi_server_connection_manager.cc',