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After the changes the test:

- Continues to test cross-site / multiple-renderer-processes case.

- Starts to verify that frame links got correctly replaced with
  local paths (this uses a separate code path from replacing links
  of other, non-frame savable resources).

- Starts to test that deduplication of savable resources happens across frames
  (deduplication got moved into the browser process in
  https://chromium.googlesource.com/chromium/src/+/6af746b740287560dbc9e85d22738000bc72b521).

BUG=526786

Review URL: https://codereview.chromium.org/1362973003

Cr-Commit-Position: refs/heads/master@{#351133}