Add a PRESUBMIT for gn check, currently only for //sky/*

sky/engine/wtf/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.
 
 visibility = ["//sky/*"]
 
 component("wtf") {
   sources = [
     "ASCIICType.h",
     "AddressSpaceRandomization.cpp",
@@ skipping 40 matching lines @@
     "DynamicAnnotations.cpp",
     "DynamicAnnotations.h",
     "FastAllocBase.h",
     "FastMalloc.cpp",
     "FastMalloc.h",
     "FilePrintStream.cpp",
     "FilePrintStream.h",
     "Float32Array.h",
     "Float64Array.h",
     "Forward.h",
-    "Functional.h",
     "GetPtr.h",
     "HashCountedSet.h",
     "HashFunctions.h",
     "HashIterators.h",
     "HashMap.h",
     "HashSet.h",
     "HashTable.cpp",
     "HashTable.h",
     "HashTableDeletedValueType.h",
     "HashTraits.h",
@@ skipping 213 matching lines @@
 
   configs += [
     "//sky/engine:config",
     "//sky/engine:non_test_config",
   ]
 
   deps = [
     ":wtf",
   ]
 }