Elide gn desc --tree output by default.

When gn's desc command is used with --tree, it prints a dependency tree. But recursively printing the dependency tree of a high-level target in Chrome prints too much output to be useful because it's printing, e.g. base and it's deps over and over (//chrome/browser-s --tree is 3210166 lines).

With this patch, a target will be recursed into the first time it's printed, but subsequent times the children will be elided with "..." This brings down //chrome/browser to 2050 lines. The previous behavior is still available (it could be useful in certain cases) via "--tree --all".

This also updates an optimization comment in the the optimization setup (optimize_max isn't just Windows-only).

R=dalecurtis@chromium.org

Review URL: https://codereview.chromium.org/437033002

git-svn-id: http://src.chromium.org/svn/trunk/src/tools/gn@287424 4ff67af0-8c30-449e-8e8b-ad334ec8d88c