Apply behaviour change fix from upstream for previous XPath change.

BUG=58731
TEST=NONE

Review URL: http://codereview.chromium.org/4027006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@63572 0039d316-1c4b-4281-b951-d872f2087c98
xmlXPathBooleanFunction(xmlXPathParserContextPtr ctxt, int nargs) {
    xmlXPathObjectPtr cur;

    CHECK_ARITY(1);
    cur = valuePop(ctxt);
    if (cur == NULL) XP_ERROR(XPATH_INVALID_OPERAND);
    cur = xmlXPathCacheConvertBoolean(ctxt->context, cur);
    valuePush(ctxt, cur);
}

xmlXPathBooleanFunction(xmlXPathParserContextPtr ctxt, int nargs) {
    xmlXPathObjectPtr cur;

    CHECK_ARITY(1);
    cur = valuePop(ctxt);
    if (cur == NULL) XP_ERROR(XPATH_INVALID_OPERAND);
    cur = xmlXPathCacheConvertBoolean(ctxt->context, cur);
    valuePush(ctxt, cur);
}
