Splice matching_files_list in $matching_files' place in gclient.py.

Based on Mark Mentovai's mail.
Review URL: http://codereview.chromium.org/164068

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@22616 0039d316-1c4b-4281-b951-d872f2087c98

gclient.py

@@ -1233,8 +1233,8 @@ class GClient(object):
       command[0] = sys.executable
 
     if '$matching_files' in command:
-      command.remove('$matching_files')
-      command.extend(matching_file_list)
+      splice_index = command.index('$matching_files')
+      command[splice_index:splice_index + 1] = matching_file_list
 
     # Use a discrete exit status code of 2 to indicate that a hook action
     # failed.  Users of this script may wish to treat hook action failures