GitLab

1. Add query params pgcl=14 and sclient=cros-launcher for launcher queries to completion server.
2. Enable ZeroSuggestProvider to process empty queries from cros launcher.
3. The above changes are only enabled when zero state is enabled by flag, which by default is off.

Bug: 854242
Change-Id: I9ca99a668b74ab642ff1d020eb14565fb4af12ff
Reviewed-on: https://chromium-review.googlesource.com/1178971Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Jenny Zhang <jennyz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590003}