Make `benchmark.mojo` resilient to incorrect trace events.

mojo/devtools/common/mojo_benchmark

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """Runner for Mojo application benchmarks."""
 
 import argparse
 import logging
 import sys
@@ skipping 71 matching lines @@
     print 'timed out' if did_time_out else 'failed'
     if return_code:
       print 'Return code: ' + str(return_code)
     print 'Output: '
     print output
     print '-' * 72
     return False
 
   # Echo measurement results.
   for line in output_lines:
-    if line.strip().startswith('measurement:'):
+    if line.strip().startswith('measurement:') or 'WARNING' in line:
       print line
   return True
 
 
 def main():
   parser = argparse.ArgumentParser(
       formatter_class=argparse.RawDescriptionHelpFormatter,
       description=_DESCRIPTION)
   parser.add_argument('benchmark_list_file', type=file,
                       help='a file listing benchmarks to run')
@@ skipping 23 matching lines @@
     measurements = benchmark_spec['measurements']
     _run_benchmark(shell, shell_args, name, app, duration, measurements,
                    cold_start=True, verbose=script_args.verbose)
     _run_benchmark(shell, shell_args, name, app, duration, measurements,
                    cold_start=False, verbose=script_args.verbose)
 
   return 0 if succeeded else 1
 
 if __name__ == '__main__':
   sys.exit(main())