Fix a typo in UserScript comment.

BUG=none

Review URL: https://chromiumcodereview.appspot.com/18179005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@209346 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/user_script.h

@@ -37,7 +37,7 @@ class UserScript {
   // Locations that user scripts can be run inside the document.
   enum RunLocation {
     UNDEFINED,
-    DOCUMENT_START,  // After the documentElemnet is created, but before
+    DOCUMENT_START,  // After the documentElement is created, but before
                      // anything else happens.
     DOCUMENT_END,  // After the entire document is parsed. Same as
                    // DOMContentLoaded.