Reland: Take 2: Force python test server output to be unbuffered, so it doesn't mix with gtest outpu

net/test/local_test_server_posix.cc

Index: net/test/local_test_server_posix.cc
diff --git a/net/test/local_test_server_posix.cc b/net/test/local_test_server_posix.cc
index 7afd422b94a6e1980a5f1e4019fbd0198ca58f8c..92439b26857ee37c35464d2a3d57719daca64538 100644
--- a/net/test/local_test_server_posix.cc
+++ b/net/test/local_test_server_posix.cc
@@ -101,6 +101,10 @@ bool LocalTestServer::LaunchPython(const FilePath& testserver_path) {
           getenv(kPythonPathEnv);
   CommandLine python_command(FilePath(FILE_PATH_LITERAL("python")));
 
+  // Use unbuffered output, so that testserver output doesn't mix with gtest
+  // output in test log files. See http://crbug.com/147368.
+  python_command.AppendArg("-u");
+
   python_command.AppendArgPath(testserver_path);
   if (!AddCommandLineArguments(&python_command))
     return false;