[Resource Timing] ACTION-33: Update spec to include a reference to what the expected behavior with plugins

After evaluating how to add a reference to the expected behavior of plugins in the Resource Timing spec, I have come to the conclusion that it may be best to not describe that behavior:


-          Plugins are not a standardized web platform feature and may not behave uniformly across user agents.

-          User agents may not even support plugins.

-          There are various types of plugin, some may or may not cause resource retrieval.

-          A plugin may or may not rely on a user agent's networking stack and may implement its own.

Considering the Resource Timing spec already makes the expected behavior of when a resource is retrieved from the networking layer or the cache clear, a plugin that modifies a page such that a resource is fetched is already covered. Other resources fetched that aren't initiated from the current document are already ignored.

In an effort to not confuse readers, I recommend the spec does not reference plugins.

Thanks,
Jatinder