Try setting fastbuild=1 on the ClangToTMac builders (except for asan)

scripts/slave/recipe_modules/chromium/config.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 pipes
 
 from slave.recipe_config import config_item_context, ConfigGroup
 from slave.recipe_config import Dict, List, Single, Static, Set, BadConf
 from slave.recipe_config_types import Path
 
@@ skipping 533 matching lines @@
   # the latest clang.
   del c.env.LLVM_FORCE_HEAD_REVISION
 
 @config_ctx(includes=['ninja', 'clang'])  # No goma.
 def clang_tot_linux(c):
   # Use ToT Clang.
   c.env.LLVM_FORCE_HEAD_REVISION = 'YES'
 
 @config_ctx(includes=['ninja', 'clang'])  # No goma.
 def clang_tot_mac(c):
-  # Use ToT Clang.
+  # Use ToT Clang and fastbuild.
   c.env.LLVM_FORCE_HEAD_REVISION = 'YES'
+  c.gyp_env.GYP_DEFINES['fastbuild'] = 1
 
 @config_ctx()
 def asan_test_batch(c):
   c.runtests.test_args.append('--test-launcher-batch-limit=1')
 
 @config_ctx(includes=['clang_tot_linux', 'asan', 'chromium_sanitizer',
                       'asan_test_batch'])
 def clang_tot_linux_asan(c):
   # Like chromium_linux_asan, without goma.
   pass
@@ skipping 264 matching lines @@
 def chromium_deterministic_build(c):
   c.gyp_env.GYP_DEFINES['dont_embed_build_metadata'] = 1
 
 @config_ctx()
 def chromium_mac_sdk_10_10(c):
   c.gyp_env.GYP_DEFINES['mac_sdk_min='] = '10.10'
 
 @config_ctx(includes=['chromium_clang'])
 def cast_linux(c):
   c.gyp_env.GYP_DEFINES['chromecast'] = 1