[Sync] Split UserEventService into interface and impl, add fake impl, add unit tests.

components/sync/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/buildflag_header.gni")
 import("//build/config/features.gni")
 import("//components/sync/protocol/protocol_sources.gni")
 import("//testing/test.gni")
 
 static_library("sync") {
@@ skipping 554 matching lines @@
     "syncable/syncable_write_transaction.h",
     "syncable/transaction_observer.h",
     "syncable/user_share.cc",
     "syncable/user_share.h",
     "syncable/write_node.cc",
     "syncable/write_node.h",
     "syncable/write_transaction.cc",
     "syncable/write_transaction.h",
     "syncable/write_transaction_info.cc",
     "syncable/write_transaction_info.h",
+    "user_events/fake_user_event_service.cc",
+    "user_events/fake_user_event_service.h",
+    "user_events/no_op_user_event_service.cc",
+    "user_events/no_op_user_event_service.h",
     "user_events/user_event_service.cc",
     "user_events/user_event_service.h",
+    "user_events/user_event_service_impl.cc",
+    "user_events/user_event_service_impl.h",
     "user_events/user_event_sync_bridge.cc",
     "user_events/user_event_sync_bridge.h",
   ]
 
   configs += [ "//build/config:precompiled_headers" ]
 
   public_deps = [
     "//base",
     "//components/sync/protocol",
     "//net",
@@ skipping 351 matching lines @@
     "syncable/directory_unittest.cc",
     "syncable/directory_unittest.h",
     "syncable/entry_kernel_unittest.cc",
     "syncable/model_type_unittest.cc",
     "syncable/nigori_util_unittest.cc",
     "syncable/parent_child_index_unittest.cc",
     "syncable/syncable_delete_journal_unittest.cc",
     "syncable/syncable_enum_conversions_unittest.cc",
     "syncable/syncable_id_unittest.cc",
     "syncable/syncable_unittest.cc",
-    "user_events/user_event_service_unittest.cc",
+    "user_events/user_event_service_impl_unittest.cc",
     "user_events/user_event_sync_bridge_unittest.cc",
   ]
 
   configs += [ "//build/config:precompiled_headers" ]
 
   data = [
     "//chrome/test/data/sync/",
     "//net/tools/testserver/",
     "//third_party/pyftpdlib/",
     "//third_party/pywebsocket/",
@@ skipping 191 matching lines @@
     deps = [
       ":fake_server_jni",
       ":sync",
       ":test_support_fake_server",
       "//base",
       "//testing/gtest",
       "//url:url",
     ]
   }
 }