Disable output buffering in devtools scripts.

mojo/devtools/common/mojo_test

Index: mojo/devtools/common/mojo_test
diff --git a/mojo/devtools/common/mojo_test b/mojo/devtools/common/mojo_test
index 59f5310e2554a1283c1800510dc597f008a40d0c..eca37f31ae5e588ee69638dadb01aeb806bc4de8 100755
--- a/mojo/devtools/common/mojo_test
+++ b/mojo/devtools/common/mojo_test
@@ -17,6 +17,7 @@ from devtoolslib import apptest_dart
 from devtoolslib import apptest_gtest
 from devtoolslib import shell_arguments
 from devtoolslib import shell_config
+from devtoolslib.utils import disable_output_buffering
 
 _DESCRIPTION = """Runner for Mojo application tests.
 
@@ -59,6 +60,7 @@ _DART_STRICT_MODE_ARG = ('--args-for=mojo:dart_content_handler '
 
 
 def main():
+  disable_output_buffering()
   parser = argparse.ArgumentParser(
       formatter_class=argparse.RawDescriptionHelpFormatter,
       description=_DESCRIPTION)
@@ -102,7 +104,6 @@ def main():
 
     _logger.info("Will start: %s" % test_name)
     print "Running %s...." % test_name,
-    sys.stdout.flush()
 
     if test_type == "dart":
       apptest_result = apptest_dart.run_dart_apptest(shell, shell_args, test,