Fix possible crash in RadioInputType::handleKeydownEvent.
Fix possible crash in RadioInputType::handleKeydownEvent.

We should protect inputElement against deletion by event handlers.

BUG=252712
TEST=none; This is not testable by a layout test

Review URL: https://chromiumcodereview.appspot.com/17568007

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@152991 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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