add support for using npm in builds
add support for using npm in builds

Use the blessed versions of node/npm that Chromium uses, and we
create a blessed bundle of node modules for our own use.  The only
modules we care about we list in the top level package.json.

We ignore package-lock.json since we're managing the node_modules
directory ourselves.

Change-Id: I4193c3fb62f09b05191d3b77710cca8affc7163b
Reviewed-on: https://chromium-review.googlesource.com/1099150
Reviewed-by: Vitaliy Shipitsyn <6f51537d61e46a00bf958b60dbef5b5870c2bf22@google.com>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm