playground: add Google analytics for Run/Share button clicks.
playground: add Google analytics for Run/Share button clicks.

Change-Id: Iad4cd4c8f0612f062c232a577eb1a95a2a912375
Reviewed-on: https://go-review.googlesource.com/10880
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

phoorichet/playground,heshed/playground,gophergala2016/playground-plus,golang/playground,neollie/playground,golang/playground,adams-sarah/playground,adams-sarah/playground,adams-sarah/playground,phoorichet/playground,golang/playground,gophergala2016/playground-plus,phoorichet/playground,gophergala2016/playground-plus,heshed/playground,neollie/playground,heshed/playground,neollie/playground