Report the HOST_BITS as 64 if the kernel is 32-bit but the CPU supports 64-bit.

scripts/slave/recipe_modules/platform/api.py

 # Copyright 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 sys
 import platform
 
 from slave import recipe_api
 
 
@@ skipping 35 matching lines @@
       self._bits = norm_bits(self._test_data.get('bits', 64))
     else:  # pragma: no cover
       # platform.machine is based on running kernel. It's possible to use 64-bit
       # kernel with 32-bit userland, e.g. to give linker slightly more memory.
       # Distinguish between different userland bitness by querying
       # the python binary.
       if (self._name == 'linux' and
           self._bits == 64 and
           platform.architecture()[0] == '32bit'):
         self._bits = 32
+      # On Mac, the inverse of the above is true: the kernel is 32-bit but the
+      # CPU and userspace both are capable of running 64-bit programs.
+      elif (self._name == 'mac' and
+            self._bits == 32 and
+            platform.architecture()[0] == '64bit'):
+        self._bits = 64
 
   @property
   @recipe_api.non_step
   def is_win(self):
     return self.name == 'win'
 
   @property
   @recipe_api.non_step
   def is_mac(self):
     return self.name == 'mac'
@@ skipping 18 matching lines @@
   @property
   @recipe_api.non_step
   def arch(self):
     return self._arch
 
   @staticmethod
   @recipe_api.non_step
   def normalize_platform_name(platform):
     """One of python's sys.platform values -> 'win', 'linux' or 'mac'."""
     return norm_plat(platform)  # pragma: no cover