Strange behavior results because SEI can change.

Example:

1. User visits page, SEI is low, initial Flash does not load.
2. User stays on page, SEI goes up.
3. Some Delayed flash plugin tries to load. Now Flash is within navigator.plugins
4. Some flash loads, some flash doesn't. Page is in an odd state

We should make either the plugin list or SEI score sticky per tab until navigation. -- or solve this some other way.