GitLab

1. Add capture-event to collect preferences' metrics for taking pictures.
2. Fix analytics.EventBuilder's dimension() method.

BUG=b:117816926
TEST=Tested by taking pictures and checking GA dashboard.

Change-Id: Ib1bd952d8d02a3742417d78f93265eb36b5cfe49
Reviewed-on: https://chromium-review.googlesource.com/c/1482358Reviewed-by: Sheng-hao Tsao <shenghao@google.com>
Commit-Queue: yuli <yuli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634991}