Fix linux_clang default try builder to only compile and not run tests.

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 310 matching lines @@
       input_api, output_api))
   results.extend(_CheckSubversionConfig(input_api, output_api))
   return results
 
 
 def GetPreferredTrySlaves(project, change):
   affected_files = change.LocalPaths()
   only_objc_files = all(f.endswith(('.mm', '.m')) for f in affected_files)
   if only_objc_files:
     return ['mac_rel']
-  preferred = ['win_rel', 'linux_rel', 'mac_rel']
-  preferred = ['win_rel', 'linux_rel', 'mac_rel', 'linux_clang']
-  if any(f.endswith(('.h', '.cc', '.cpp', '.cxx')) for f in affected_files):
-    preferred.append('linux_clang')
+  preferred = ['win_rel', 'linux_rel', 'mac_rel', 'linux_clang:compile']
   aura_re = '_aura[^/]*[.][^/]*'
   if any(re.search(aura_re, f) for f in affected_files):
     preferred.append('linux_chromeos')
   # Nothing in chrome/
   android_re_list = ('^base/',
                      '^build/common.gypi$',
                      '^content/',
                      '^ipc/',
                      '^jingle/',
                      '^media/',
                      '^net/',
                      '^sql/')
   # Nothing that looks like win-only or aura-only
   win_re = '_win\.(cc|h)$'
   possibly_android = True
   for non_android_re in (aura_re, win_re):
     if all(re.search(non_android_re, f) for f in affected_files):
       possibly_android = False
       break
   if possibly_android:
     for f in change.AffectedFiles():
       if any(re.search(r, f.LocalPath()) for r in android_re_list):
         preferred.append('android')
         break
   return preferred