Refactor print-layout-test-times and add unit tests.

Tools/Scripts/webkitpy/common/system/systemhost.py

Index: Tools/Scripts/webkitpy/common/system/systemhost.py
diff --git a/Tools/Scripts/webkitpy/common/system/systemhost.py b/Tools/Scripts/webkitpy/common/system/systemhost.py
index 3b4439ee4785bdc220ee72333179268499ad12a3..52b88d6fcc1d525a4ac3586c4a0e186a9942bd2a 100644
--- a/Tools/Scripts/webkitpy/common/system/systemhost.py
+++ b/Tools/Scripts/webkitpy/common/system/systemhost.py
@@ -43,3 +43,12 @@ class SystemHost(object):
 
     def copy_current_environment(self):
         return environment.Environment(os.environ.copy())
+
+    def print_(self, *args, **kwargs):
+        sep = kwargs.get('sep', ' ')
+        end = kwargs.get('end', '\n')
+        file = kwargs.get('file', None)
+        stderr = kwargs.get('stderr', False)
+
+        file = file or (sys.stderr if stderr else sys.stdout)
+        file.write(sep.join([str(arg) for arg in args]) + end)