Allocator shim skeleton + Linux impl behind a build flag

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 1321 matching lines @@
     'android_lint%': 1,
 
     # Although base/allocator lets you select a heap library via an
     # environment variable, the libcmt shim it uses sometimes gets in
     # the way.  To disable it entirely, and switch to normal msvcrt, do e.g.
     #  'win_use_allocator_shim': 0,
     #  'win_release_RuntimeLibrary': 2
     # to ~/.gyp/include.gypi, gclient runhooks --force, and do a release build.
     'win_use_allocator_shim%': 1, # 1 = shim allocator via libcmt; 0 = msvcrt
 
+    # Enables the unified allocator shim (experimental) which routes all the
+    # alloc calls to base/. Right now is supported on Linux Desktop only.
+    # http://crbug.com/550886 .
+    'use_experimental_allocator_shim%': 0,
+
     # TODO(bradnelson): eliminate this when possible.
     # To allow local gyp files to prevent release.vsprops from being included.
     # Yes(1) means include release.vsprops.
     # Once all vsprops settings are migrated into gyp, this can go away.
     'msvs_use_common_release%': 1,
 
     # TODO(bradnelson): eliminate this when possible.
     # To allow local gyp files to override additional linker options for msvs.
     # Yes(1) means set use the common linker options.
     'msvs_use_common_linker_extras%': 1,
@@ skipping 5001 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }