Added os to input_api

BUG=
R=maruel@chromium.org

Review URL: https://codereview.chromium.org/614413003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@292291 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/presubmit_support.py b/presubmit_support.py
index e929e31..b386524 100755
--- a/presubmit_support.py
+++ b/presubmit_support.py
@@ -292,6 +292,7 @@
     self.os_listdir = os.listdir
     self.os_walk = os.walk
     self.os_path = os.path
+    self.os_stat = os.stat
     self.pickle = pickle
     self.marshal = marshal
     self.re = re