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This incorporats with dgozman's comments in crrev.com/c/1004890
- Change "from SignedExchange" to "from signed-exchange" in NetworkRequestNode.
- Show the signed exchagne url as the initiator of certificate request.
- Show "from signed-exchange" in the headers tab of the inner request.
- Add "View request" link in the preview tab of signed exchange to show the inner request.
- Add "Learn more" link in the preview tab of signed exchange.

Bug: 830505
Change-Id: Ica7ae52e563efb283c600c812be196951a12a336
Reviewed-on: https://chromium-review.googlesource.com/1065558
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Kunihiko Sakamoto <ksakamoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560287}