Add doodle sharing to local NTP. Sharing consists of a sharing button and a sharing dialog box. Also includes browser tests.

Bug:896461

-Enable using the Google local NTP -> Enabled
-Enable doodles on the local NTP -> Enabled
-?force-doodle=0 (for simple) or ?force-doodle=1 (for animated)

Test: Set the following flags in chrome://flags:
Change-Id: If900a18e2cada746132d894aa104f273f914bd90
Reviewed-on: https://chromium-review.googlesource.com/c/1330356
Reviewed-by: Kyle Milka <kmilka@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: David Lu <davidluphd@google.com>
Cr-Commit-Position: refs/heads/master@{#614505}
13 files changed