[Rich Entity Suggest] add flag for omnibox-rich-entity-suggest

This CL adds a flag for enable/disable the GUI enhancements for rich
entity suggestions in the omnibox. The default value is Disabled.

As of this CL, the flag has no effect.

Bug: 798630
Change-Id: I9e3ca0660965019dfbab16d2b98255d8cf7128c0
Reviewed-on: https://chromium-review.googlesource.com/848236
Commit-Queue: Dave Schuyler <[email protected]>
Reviewed-by: Tommy Li <[email protected]>
Cr-Commit-Position: refs/heads/master@{#527085}
6 files changed