Upgrade a TextIterator ASSERT to a RELEASE_ASSERT as a defensive measure.

BUG=156930,177197
R=inferno@chromium.org

Review URL: https://codereview.chromium.org/15057010

git-svn-id: svn://svn.chromium.org/blink/trunk@150123 bbb929c8-8fbe-4397-9dbb-9b2b20218538
PassRefPtr<Range> CharacterIterator::range() const
{
    RefPtr<Range> r = m_textIterator.range();
    if (!m_textIterator.atEnd()) {
        if (m_textIterator.length() <= 1) {
            ASSERT(m_runOffset == 0);
        } else {
            Node* n = r->startContainer();
            ASSERT(n == r->endContainer());
            int offset = r->startOffset() + m_runOffset;
            r->setStart(n, offset, ASSERT_NO_EXCEPTION);
            r->setEnd(n, offset + 1, ASSERT_NO_EXCEPTION);
        }
    }
    return r.release();
}

PassRefPtr<Range> CharacterIterator::range() const
{
    RefPtr<Range> r = m_textIterator.range();
    if (!m_textIterator.atEnd()) {
        if (m_textIterator.length() <= 1) {
            ASSERT(m_runOffset == 0);
        } else {
            Node* n = r->startContainer();
            ASSERT(n == r->endContainer());
            int offset = r->startOffset() + m_runOffset;
            r->setStart(n, offset, ASSERT_NO_EXCEPTION);
            r->setEnd(n, offset + 1, ASSERT_NO_EXCEPTION);
        }
    }
    return r.release();
}
