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This adds an integration test to check that DocumentsProvider
implementation correctly interact with ARC-related services in
Chrome side by marking ARC as available for testing and mocking
FileSystemInstance (Mojo interface to interact with ARC container).

Bug: 923991
Test: Run browset_tests --gtest_filter=QuickView/FilesAppBrowserTest.Test/openQuickView*
Change-Id: I72cf99449880aea0acc33cc7f679656ea4e396f8
Reviewed-on: https://chromium-review.googlesource.com/c/1483697
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634958}