Revert of Move gn _run target generation into test().

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/config/features.gni")
 import("//sync/protocol/protocol_sources.gni")
 import("//testing/test.gni")
 
 component("sync") {
   public_deps = [
@@ skipping 592 matching lines @@
 
   defines = [ "SYNC_TEST" ]
 
   public_deps = [
     "//base",
     "//sync",
     "//testing/gmock",
   ]
 }
 
+# TODO(GYP): Delete this after we've converted everything to GN.
+# The _run targets exist only for compatibility w/ GYP.
+group("sync_unit_tests_run") {
+  testonly = true
+  deps = [
+    ":sync_unit_tests",
+  ]
+}
+
 # GYP version: sync/sync_tests.gypi:sync_unit_tests
 test("sync_unit_tests") {
   sources = [
     "api/attachments/attachment_id_unittest.cc",
     "api/attachments/attachment_metadata_unittest.cc",
     "api/attachments/attachment_unittest.cc",
     "api/entity_data_unittest.cc",
     "api/sync_change_unittest.cc",
     "api/sync_data_unittest.cc",
     "api/sync_error_unittest.cc",
@@ skipping 267 matching lines @@
       ":fake_server_jni",
       ":sync_core",
       ":test_support_sync_fake_server",
       "//base",
       "//sync/protocol:protocol",
       "//testing/gtest",
       "//url:url",
     ]
   }
 }