Remove allocator_extension_thunks since this layer is not required

base/BUILD.gn

 # Copyright (c) 2013 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/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 if (is_android) {
@@ skipping 681 matching lines @@
 
   data = []
 
   configs += [
     ":base_flags",
     ":base_implementation",
     "//build/config:precompiled_headers",
   ]
 
   deps = [
-    "//base/allocator:extension_thunks",
     "//base/third_party/dynamic_annotations",
     "//third_party/modp_b64",
   ]
 
   public_deps = [
     ":base_paths",
     ":base_static",
     "//base/debug",
     "//base/json",
     "//base/memory",
@@ skipping 1035 matching lines @@
 
   # GYP: //base.gyp:base_java_unittest_support
   android_library("base_java_unittest_support") {
     deps = [
       ":base_java",
     ]
     java_files =
         [ "test/android/java/src/org/chromium/base/ContentUriTestUtils.java" ]
   }
 }