Split //ui/events/devices into two targets.

ui/events/x/BUILD.gn

 # Copyright 2016 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.
 
 component("x") {
+  output_name = "events_x"
   sources = [
     "events_x_export.h",
     "events_x_utils.cc",
     "events_x_utils.h",
   ]
   defines = [ "EVENTS_X_IMPLEMENTATION" ]
   deps = [
     "//base",
     "//skia",
     "//ui/events:events_base",
     "//ui/events/devices",
+    "//ui/events/devices/x11",
     "//ui/gfx/x",
   ]
   configs += [ "//build/config/linux:x11" ]
 }