Fix launch script for internal slaves

BUG=skia:761

Review URL: https://codereview.chromium.org/639823007
Adding session state and confirmation to login handling.

https://developers.google.com/accounts/docs/OAuth2Login#createxsrftoken

BUG=skia:

Review URL: https://codereview.chromium.org/653443003
perf: Add Squid section to DESIGN doc.

BUG=None
TEST=None
R=jcgregorio@google.com

Review URL: https://codereview.chromium.org/624793002
perf: Upgrade go tool to version 1.3.3

BUG=None
TEST=None
R=jcgregorio@google.com

Review URL: https://codereview.chromium.org/621183002