GTTF: Increase percentage of manual try jobs going to recipe-based trybots.

PRESUBMIT.py

 # 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.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 1435 matching lines @@
 
   # The AOSP bot doesn't build the chrome/ layer, so ignore any changes to it
   # unless they're .gyp(i) files as changes to those files can break the gyp
   # step on that bot.
   if (not all(re.search('^chrome', f) for f in files) or
       any(re.search('\.gypi?$', f) for f in files)):
     trybots.extend(GetDefaultTryConfigs(['android_aosp']))
 
   # Experimental recipe-based Chromium trybots. To avoid possible capacity
   # problems, only enable for a small percentage of try runs.
-  if random.random() < 0.1:
+  if random.random() < 0.25:
     trybots.extend(GetDefaultTryConfigs([
         'linux_chromium_dbg',
         'linux_chromium_rel',
         'mac_chromium_dbg',
         'mac_chromium_rel',
     ]))
 
   return trybots