Remove ENABLE(INSTANCE_COUNTER) code.

third_party/WebKit/Source/platform/wtf/BUILD.gn

 # Copyright 2017 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.
 
 assert(!is_ios)
 
 import("//testing/test.gni")
 import("//third_party/WebKit/Source/config.gni")
 
 visibility = [
@@ skipping 72 matching lines @@
     "HashCountedSet.h",
     "HashFunctions.h",
     "HashIterators.h",
     "HashMap.h",
     "HashSet.h",
     "HashTable.cpp",
     "HashTable.h",
     "HashTableDeletedValueType.h",
     "HashTraits.h",
     "HexNumber.h",
-    "InstanceCounter.cpp",
-    "InstanceCounter.h",
     "LeakAnnotations.h",
     "LinkedHashSet.h",
     "ListHashSet.h",
     "Locker.h",
     "MathExtras.h",
     "NonCopyingSort.h",
     "Noncopyable.h",
     "NotFound.h",
     "Optional.h",
     "PassRefPtr.h",
@@ skipping 268 matching lines @@
   ]
 
   deps = [
     ":wtf",
     "//base",
     "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }