GN: Make content_shell and webkit_unit_tests work in component build

ui/wm/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.
 
 component("wm") {
   sources = [
     "core/accelerator_delegate.h",
     "core/accelerator_filter.cc",
     "core/accelerator_filter.h",
     "core/base_focus_rules.h",
@@ skipping 61 matching lines @@
 
   defines = [ "WM_IMPLEMENTATION" ]
 
   deps = [
     "//base",
     "//skia",
     "//ui/aura",
     "//ui/base",
     "//ui/compositor",
     "//ui/events",
+    "//ui/events/platform",
     "//ui/events:events_base",
     "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/resources",
   ]
 }
 
 static_library("test_support") {
   sources = [
@@ skipping 44 matching lines @@
     "//ui/compositor",
     "//ui/events",
     "//ui/events:events_base",
     "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
 }
 
 }