Disable output buffering in devtools scripts.

mojo/devtools/common/mojo_benchmark

Index: mojo/devtools/common/mojo_benchmark
diff --git a/mojo/devtools/common/mojo_benchmark b/mojo/devtools/common/mojo_benchmark
index e01ff627d22e63ea5633b9682e801f7b04cf3655..0c1dcd939db2171c3a159bd5b4b2dcf12798150a 100755
--- a/mojo/devtools/common/mojo_benchmark
+++ b/mojo/devtools/common/mojo_benchmark
@@ -15,6 +15,7 @@ from devtoolslib import benchmark
 from devtoolslib import perf_dashboard
 from devtoolslib import shell_arguments
 from devtoolslib import shell_config
+from devtoolslib.utils import disable_output_buffering
 
 
 _DESCRIPTION = """Runner for Mojo application benchmarks.
@@ -145,6 +146,7 @@ def _argparse_aggregate_type(value):
 
 
 def main():
+  disable_output_buffering()
   parser = argparse.ArgumentParser(
       formatter_class=argparse.RawDescriptionHelpFormatter,
       description=_DESCRIPTION)