[Sync] Fix test support targets + duplicate namespaces.

extensions/BUILD.gn

 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//testing/test.gni")
 import("//tools/grit/grit_rule.gni")
 import("//tools/grit/repack.gni")
 
 assert(enable_extensions)
 
 group("extensions_resources") {
@@ skipping 262 matching lines @@
     "//chrome/renderer",
     "//components/autofill/content/browser:risk_proto",
     "//components/autofill/content/renderer:test_support",
     "//components/captive_portal:test_support",
     "//components/dom_distiller/content/browser",
     "//components/dom_distiller/core:test_support",
     "//components/guest_view/browser:test_support",
     "//components/resources",
     "//components/strings",
     "//components/sync",
-    "//components/sync:test_support_sync_model",
+    "//components/sync:test_support_model",
     "//components/translate/core/common",
     "//crypto:platform",
     "//crypto:test_support",
     "//device/bluetooth:mocks",
     "//device/serial:test_support",
     "//extensions/common/api",
     "//google_apis:test_support",
     "//media",
     "//media/base:test_support",
     "//media/cast:test_support",
@@ skipping 55 matching lines @@
     "//testing/gtest",
     "//third_party/hunspell",
     "//third_party/icu",
     "//third_party/libpng",
     "//third_party/zlib",
     "//ui/base:test_support",
     "//ui/resources:ui_test_pak",
     "//ui/web_dialogs:test_support",
   ]
 }