Convert some GN test support targets to static libs.

components/storage_monitor/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")
 
 # GYP version: components/storage_monitor.gypi:storage_monitor
-source_set("storage_monitor") {
+static_library("storage_monitor") {
   sources = [
     "image_capture_device.h",
     "image_capture_device.mm",
     "image_capture_device_manager.h",
     "image_capture_device_manager.mm",
     "media_storage_util.cc",
     "media_storage_util.h",
     "media_transfer_protocol_device_observer_linux.cc",
     "media_transfer_protocol_device_observer_linux.h",
     "mtab_watcher_linux.cc",
@@ skipping 62 matching lines @@
       "mtab_watcher_linux.cc",
       "mtab_watcher_linux.h",
       "storage_monitor_linux.cc",
       "storage_monitor_linux.h",
     ]
     deps += [ "//chromeos" ]
   }
 }
 
 # GYP version: components/storage_monitor.gypi:storage_monitor_test_support
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = [
     "mock_removable_storage_observer.cc",
     "mock_removable_storage_observer.h",
     "test_media_transfer_protocol_manager_linux.cc",
     "test_media_transfer_protocol_manager_linux.h",
     "test_portable_device_watcher_win.cc",
     "test_portable_device_watcher_win.h",
     "test_storage_monitor.cc",
     "test_storage_monitor.h",
@@ skipping 51 matching lines @@
     }
   }
   if (is_chromeos) {
     sources += [ "storage_monitor_chromeos_unittest.cc" ]
     deps += [
       "//chromeos:test_support",
       "//testing/gmock",
     ]
   }
 }