Always use --leg_only option.

dart/frog/scripts/buildbot_annotated_steps.py

 #!/usr/bin/python
 
 # 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.
 
 """Dart frog buildbot steps
 
 Runs tests for the frog compiler (running on the vm or the self-hosting version)
 """
@@ skipping 75 matching lines @@
       [sys.executable, '../tools/build.py', '--mode=' + testpy_mode],
       env=NO_COLOR_ENV) != 0:
     return 1
 
   if arch != 'frogium': # frog and frogsh
     if TestStep("frog", testpy_mode, arch,
                   ['language', 'corelib', 'isolate', 'frog',
                    'leg', 'leg_only', 'peg', 'await'], flags) != 0:
       return 1
 
-    leg_tests = ['language', 'corelib', 'leg', 'leg_only']
+    leg_tests = ['language', 'corelib', 'leg_only']
     if TestStep("leg", testpy_mode, 'leg', leg_tests, flags) != 0:
       return 1
+
+    # Leg isn't self-hosted (yet) so we run the unit tests on the VM.
+    if TestStep("leg", testpy_mode, 'vm', ['leg'], flags) != 0:
+      return 1
   else:
     if (TestStep("browser", testpy_mode, 'frogium',
           ['client', 'language', 'corelib', 'isolate', 'frog',
            'leg', 'peg', 'await'], flags) != 0):
       return 1
 
   return 0
 
 def main():
   print 'main'
   if len(sys.argv) == 0:
     print 'Script pathname not known, giving up.'
     return 1
 
   arch, mode = GetBuildInfo()
   print "arch: %s, mode: %s" % (arch, mode)
   if arch is None:
     return 1
 
   status = TestFrog(arch, mode)
   if status != 0:
     print '@@@STEP_FAILURE@@@'
   return status
 
 
 if __name__ == '__main__':
   sys.exit(main())