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- Adding persistence via the keychain to remember secrets.
- Hide the checkbox based on host reported capabilities.

Change-Id: Ibf18726fd97636bd880395d44d6dc92a54ff1b69
Reviewed-on: https://chromium-review.googlesource.com/565660Reviewed-by: Yuwei Huang <yuweih@chromium.org>
Commit-Queue: Scott Nichols <nicholss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485946}