Re-land 714393002 after fixing android build.

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 = [
     "AddressSpaceRandomization.cpp",
     "AddressSpaceRandomization.h",
@@ skipping 92 matching lines @@
     "ListHashSet.h",
     "Locker.h",
     "MainThread.cpp",
     "MainThread.h",
     "MallocZoneSupport.h",
     "MathExtras.h",
     "MessageQueue.h",
     "Noncopyable.h",
     "NonCopyingSort.h",
     "NotFound.h",
-    "NullPtr.cpp",
     "NullPtr.h",
     "OwnPtr.h",
     "OwnPtrCommon.h",
     "PageAllocator.cpp",
     "PageAllocator.h",
     "PartitionAlloc.cpp",
     "PartitionAlloc.h",
     "PassOwnPtr.h",
     "PassRefPtr.h",
     "PassTraits.h",
@@ skipping 176 matching lines @@
 
   configs += [
     "//sky/engine:config",
     "//sky/engine:non_test_config",
   ]
 
   deps = [
     ":wtf",
   ]
 }