Add EarlGrey tests for chrome://inspect page.

Bug: 899851
Change-Id: Ia5f1191f6fff25ec16938b542443f27a17bd8d2f
Reviewed-on: https://chromium-review.googlesource.com/c/1414290
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623899}
6 files changed