Add linux_shared to the default try set!

PRESUBMIT.py

 # Copyright (c) 2011 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 320 matching lines @@
       input_api, output_api))
   results.extend(_CheckSubversionConfig(input_api, output_api))
   return results
 
 
 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']
+  preferred = ['win_rel', 'linux_rel', 'mac_rel', 'linux_shared']
   aura_re = '_aura[^/]*[.][^/]*'
   if any(re.search(aura_re, f.LocalPath()) for f in change.AffectedFiles()):
     preferred.append('linux_chromeos_aura:compile')
   return preferred