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This adds some simple navigation instrumentation tests, which should
make sure WebLayer shell is basically working as expected.

Change-Id: I656a68b7202e86676a2ce75e79e7ef1f418d3772
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1801746Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#696841}