When we fixed  issue 667481 , we lost the ability to log interventions if the main frame is remote.

From https://codereview.chromium.org/2522633003#msg26:
-----------------------------------------------------
On 2016/12/27 07:56:38, dcheng wrote:
> I might be missing something, but how are the interventions reported to the
> local root here? It seems like it just isn't reported at all in this case.

I think you're right -- we just drop the logs that are generated from
non-main-frame renderers.

I looked into fixing this but got a bit stuck: is there some object that
corresponds with the local root(s) of each renderer? I couldn't find a way to
get from WebViewImpl to the local root without recursing into the frame tree
which seems yucky. Can you think of a better idea?
-----------------------------------------------------

I think what we'll need to do is make sure that intervention reporting is plumbed through a frame-associated method, instead of the WebView. I'm not sure how much more complicated that will make things, but that's the right fix.