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 - Adds a new Context Menu with a "Copy" action.
 - Wraps the old implementation with a feature flag check.
 - Adds metrics for the new context menu and its action.

Bug: 1093302
Change-Id: Ib814b1c16b18f2855a6cc8ad6d9f425a230ce8be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2325172
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Sebastien Lalancette <seblalancette@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793174}