Convert some GN test support targets to static libs.

components/sync_sessions/BUILD.gn

 # Copyright 2015 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.
 
 # GYP version: components/sync_sessions.gypi:sync_sessions
-source_set("sync_sessions") {
+static_library("sync_sessions") {
   sources = [
     "favicon_cache.cc",
     "favicon_cache.h",
     "local_session_event_router.h",
     "open_tabs_ui_delegate.cc",
     "open_tabs_ui_delegate.h",
     "revisit/bookmarks_by_url_provider_impl.cc",
     "revisit/bookmarks_by_url_provider_impl.h",
     "revisit/bookmarks_page_revisit_observer.cc",
     "revisit/bookmarks_page_revisit_observer.h",
@@ skipping 41 matching lines @@
     "//components/sessions",
     "//components/sync_driver",
     "//components/variations",
     "//sync",
     "//ui/base:base",
     "//ui/gfx",
     "//url",
   ]
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = [
     "fake_sync_sessions_client.cc",
     "fake_sync_sessions_client.h",
   ]
 
   public_deps = [
     ":sync_sessions",
     "//base",
     "//url",
@@ skipping 29 matching lines @@
     "//components/sync_driver",
     "//components/sync_driver:test_support",
     "//sync",
     "//sync:test_support_sync_api",
     "//testing/gmock",
     "//testing/gtest",
     "//ui/base:base",
     "//url",
   ]
 }