Revised CL for customisable logging (replacing printfs).

runtime/bin/log_macos.cc

Index: runtime/bin/log_macos.cc
===================================================================
--- runtime/bin/log_macos.cc	(revision 0)
+++ runtime/bin/log_macos.cc	(revision 0)
@@ -0,0 +1,17 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "bin/log.h"
+
+#include <stdio.h>
+
+void Log::VPrint(const char* format, va_list args) {
+  vfprintf(stdout, format, args);
+  fflush(stdout);
+}
+
+void Log::VPrintErr(const char* format, va_list args) {
+  vfprintf(stderr, format, args);
+  fflush(stderr);
+}