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According to proposal, when the feature flag is enabled, the context
menu for Homebutton will be changed from "Remove" to "Edit Homepage",
and launch HomeSettings.

Change-Id: If416a585200a7b854cdd66f4c0b1f0982983fef9
Bug: 1036470
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994099Reviewed-by: Natalie Chouinard <chouinard@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Wenyu Fu <wenyufu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733052}