Remove tcmalloc when not being used. Restore shim on Windows.

base/allocator/allocator_shim.h

-// Copyright (c) 2012 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.
-
-#ifndef BASE_ALLOCATOR_ALLOCATOR_SHIM_H_
-#define BASE_ALLOCATOR_ALLOCATOR_SHIM_H_
-
-#include <stddef.h>
-
-namespace base {
-namespace allocator {
-
-// Resets the environment variable CHROME_ALLOCATOR to specify the choice to
-// be used by subprocesses.  Priority is given to the current value of
-// CHROME_ALLOCATOR_2 (if specified), then CHROME_ALLOCATOR (if specified), and
-// then a default value (typically set to TCMALLOC).
-void SetupSubprocessAllocator();
-
-// Expose some of tcmalloc functions for test.
-void* TCMallocDoMallocForTest(size_t size);
-void TCMallocDoFreeForTest(void* ptr);
-size_t ExcludeSpaceForMarkForTest(size_t size);
-
-}  // namespace allocator.
-}  // namespace base.
-
-#endif   // BASE_ALLOCATOR_ALLOCATOR_SHIM_H_