Attempt to address libxml crash.

BUG=129930
Review URL: https://chromiumcodereview.appspot.com/10458051

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@142822 0039d316-1c4b-4281-b951-d872f2087c98
void xmlCleanupGlobals(void)
{
    if (xmlThrDefMutex != NULL) {
	xmlFreeMutex(xmlThrDefMutex);
	xmlThrDefMutex = NULL;
    }
    __xmlGlobalInitMutexDestroy();
}

void xmlCleanupGlobals(void)
{
    if (xmlThrDefMutex != NULL) {
	xmlFreeMutex(xmlThrDefMutex);
	xmlThrDefMutex = NULL;
    }
    __xmlGlobalInitMutexDestroy();
}
