GN fixes for the Windows build.

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
 static_library("storage_monitor") {
   sources = [
     "image_capture_device.h",
@@ skipping 48 matching lines @@
       "//device/media_transfer_protocol",
       "//device/media_transfer_protocol:mtp_file_entry_proto",
       "//device/media_transfer_protocol:mtp_storage_info_proto",
     ]
   }
 
   if (use_udev) {
     deps += [
       "//device/udev_linux",
     ]
-  } else {
+  } else if (is_linux) {
+    # These were already removed for non-Linux.
     sources -= [
       "storage_monitor_linux.cc",
       "storage_monitor_linux.h",
       "udev_util_linux.cc",
       "udev_util_linux.h",
     ]
   }
 
   if (is_chromeos) {
     sources -= [
@@ skipping 27 matching lines @@
     ":storage_monitor",
   ]
 
   if (is_linux) {
     deps += [
       "//device/media_transfer_protocol",
       "//device/media_transfer_protocol:mtp_file_entry_proto",
     ]
   }
 }