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When bookmarks experiment is enabled existing code will add a command line flag that will allow opt-out to be shown on a chrome:flags page.
On Chrome OS at time of login if they see command line flag from any experiment they restart browser. It creates delay and user will see a black screen for a couple seconds. It happens on every login, not only the first one.
I talked to CrOS devs and they strongly discourage from using command line flags.
So for Chrome OS only do not add flag to command line but still keep it in a flag_storage. Use flag storage when need to check if flag is set.

BUG=

Review URL: https://codereview.chromium.org/578333003

Cr-Commit-Position: refs/heads/master@{#296504}