Change WebContentsObserver::SubresourceResponseStarted to load complete

Changing the WebContentsObserver::SubresourceResponseStarted to
SubresourceLoadComplete. This is going to be used to support page load
metrics with the network service.

Note that SubresourceResponseStarted in frame.mojom is kept, as it is
used by the SSLManager. It's implementation is kept in WebContentsImpl
and its parameters are changed to only what's needed for that use case.

Bug: 816684
Change-Id: I78fa4b0d7f44cfb0a5e98a7fc008fb7a17f8aae4
Reviewed-on: https://chromium-review.googlesource.com/967370
Commit-Queue: Jay Civelli <[email protected]>
Reviewed-by: Varun Khaneja <[email protected]>
Reviewed-by: John Abd-El-Malek <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Reviewed-by: Conley Owens <[email protected]>
Cr-Commit-Position: refs/heads/master@{#545558}
16 files changed