The `http_api_debug` hook isn't called for all HTTP requests

[johnbillion]

In WP_Http::_dispatch_request(), the http_api_debug action isn't called if there are no available transports for the request. This means we miss a situation that is ripe for debugging.

Edit: There's more. See my comments below.

25747.diff​ (best viewed without whitespace changes) alters _dispatch_request() so it doesn't return the WP_Error immediately. It then gets passed to the http_api_debug hook as expected.

Anything that's hooking into this hook will need to ensure it handles boolean false as the $class parameter, as well as a string.

There are actually several places where an HTTP request's return value doesn't trigger the http_api_debug action. None of the following responses trigger it:

• Anything short-circuiting requests with the pre_http_request filter (​here).
• Invalid URLs (​here).
• Blocked requests (​here).
• Unwritable directories when streaming (​here).

We might need a little refactoring here, or a helper method to trigger this action.

Bump

25747.2.diff​ is a partial patch that I've had sitting around for ages. Probably needs some more work. And tests.