Make the .test_cases file more compact when large

tools/isolate/trace_test_cases.py

 #!/usr/bin/env python
 # 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.
 
 """A manual version of trace_inputs.py that is specialized in tracing each
 google-test test case individually.
 
 This is mainly written to work around bugs in strace w.r.t. browser_tests.
 """
@@ skipping 130 matching lines @@
     print 'Got a timeout while processing a task item %s' % e
     # Be sure to stop the pool on exception.
     pool.terminate()
     return 1
   except Exception, e:
     # Be sure to stop the pool on exception.
     pool.terminate()
     raise
   finally:
     with open('%s.test_cases' % executable, 'w') as f:
-      json.dump(out, f, indent=2, sort_keys=True)
+      if len(out) > 20:
+        # Pack it dense since the file is going to be pretty large.
+        json.dump(out, f, separators=(',',':'))
+      else:
+        # Keep it human readable.
+        json.dump(out, f, indent=2, sort_keys=True)
     pool.close()
     pool.join()
 
 
 def main():
   """CLI frontend to validate arguments."""
   parser = optparse.OptionParser(
       usage='%prog <options> [gtest]')
   parser.allow_interspersed_args = False
   parser.add_option(
@@ skipping 42 matching lines @@
       options.cwd,
       options.product_dir,
       options.leak,
       options.skip,
       options.jobs,
       options.timeout)
 
 
 if __name__ == '__main__':
   sys.exit(main())