Fix tracking of the id attribute string if it is shared across elements.

The patch to remove AtomicStringImpl:
http://src.chromium.org/viewvc/blink?view=rev&rev=154790

Exposed a lifetime issue with strings for id attributes. We simply need to use
AtomicString.

BUG=290566

Review URL: https://codereview.chromium.org/33793004

git-svn-id: svn://svn.chromium.org/blink/trunk@160250 bbb929c8-8fbe-4397-9dbb-9b2b20218538
inline void DialogHandler::dialogCreated(DOMWindow* dialogFrame)
{
    m_dialogContext = dialogFrame->frame() ? dialogFrame->frame()->script()->currentWorldContext() : v8::Local<v8::Context>();
    if (m_dialogContext.IsEmpty())
        return;
    if (m_dialogArguments.IsEmpty())
        return;
    v8::Context::Scope scope(m_dialogContext);
    m_dialogContext->Global()->Set(v8::String::NewSymbol("dialogArguments"), m_dialogArguments);
}

inline void DialogHandler::dialogCreated(DOMWindow* dialogFrame)
{
    m_dialogContext = dialogFrame->frame() ? dialogFrame->frame()->script()->currentWorldContext() : v8::Local<v8::Context>();
    if (m_dialogContext.IsEmpty())
        return;
    if (m_dialogArguments.IsEmpty())
        return;
    v8::Context::Scope scope(m_dialogContext);
    m_dialogContext->Global()->Set(v8::String::NewSymbol("dialogArguments"), m_dialogArguments);
}
