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
static bool shouldEmitNewlineForNode(Node* node, bool emitsOriginalText)
{
    RenderObject* renderer = node->renderer();

    if (renderer ? !renderer->isBR() : !node->hasTagName(brTag))
        return false;
    return emitsOriginalText || !(node->isInShadowTree() && node->shadowHost()->toInputElement());
}

static bool shouldEmitNewlineForNode(Node* node, bool emitsOriginalText)
{
    RenderObject* renderer = node->renderer();

    if (renderer ? !renderer->isBR() : !node->hasTagName(brTag))
        return false;
    return emitsOriginalText || !(node->isInShadowTree() && node->shadowHost()->toInputElement());
}
