Tries to fetch plugins information once and again when plugin process fails

[Claudio Saavedra]

This is problematic when GetPlugins fails somehow:

void WebPlatformStrategies::populatePluginCache()
{
    if (m_pluginCacheIsPopulated)
        return;

    ASSERT(m_cachedPlugins.isEmpty());

    // FIXME: Should we do something in case of error here?
    if
(!WebProcess::shared().parentProcessConnection()->sendSync(Messages::WebProcessProxy::GetPlugins(m_shouldRefreshPlugins),
Messages::WebProcessProxy::GetPlugins::Reply(m_cachedPlugins,
m_cachedApplicationPlugins), 0))
        return;

    m_shouldRefreshPlugins = false;
    m_pluginCacheIsPopulated = true;
}

If this fails we shouldn't be checking once an again.