Add a "when" parameter to Chain.capture().

This makes it easy for users to switch capturing on and off based on
whether they're in a debug or development mode.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1583483003 .
4 files changed
tree: 32d76574cc22802dfb2fc2f50b98c117c3621b2d
  1. pkgs/