Revert back to use exec() instead of execfile().

It seems execfile() has different properties than exec().

TEST=none
BUG=none

Review URL: http://codereview.chromium.org/3448001

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@59407 0039d316-1c4b-4281-b951-d872f2087c98

drover.py

@@ -403,7 +403,9 @@ def drover(options, args):
   global file_pattern_
   if os.path.exists("drover.properties"):
     FILE_PATTERN = file_pattern_
-    execfile("drover.properties")
+    f = open("drover.properties")
+    exec(f)
+    f.close()
     if FILE_PATTERN:
       file_pattern_ = FILE_PATTERN