Presubmit change to add android trybots when needed.

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 324 matching lines @@
 
 def GetPreferredTrySlaves(project, change):
   only_objc_files = all(
       f.LocalPath().endswith(('.mm', '.m')) for f in change.AffectedFiles())
   if only_objc_files:
     return ['mac_rel']
   preferred = ['win_rel', 'linux_rel', 'mac_rel']
   aura_re = '_aura[^/]*[.][^/]*'
   if any(re.search(aura_re, f.LocalPath()) for f in change.AffectedFiles()):
     preferred.append('linux_chromeos')
+  # For bringup (staging of upstream work) we must be careful to not
+  # overload Android infrastructure.  Keeping Android try decisions in a
+  # single location (instead of adding conditionals in base/, net/, ...)
+  # will help us avoid doing so.  For example, we are starting off with
+  # 2 trybots (compared against ~45 for Mac and Linux).
+  # If any file matches something compiled on the main waterfall
+  # android builder, use the android try server.
+  android_re_list = ('^base/', '^ipc/', '^net/', '^sql/', '^jingle/',
+                     '^build/common.gypi$')
+  for f in change.AffectedFiles():
+    if any(re.search(r, f.LocalPath()) for r in android_re_list):
+      preferred.append('android')
+      break
   return preferred