Don't precompile Dart2JS for pull requests, instead serve the dart
sources with pub serve. We were already testing with Dartium so
all we lose is some test coverage of defects exposed only by the
Dart2JS transpiler.
This still runs the dart transformer.
Fixes#3030
* `npm install` now does a full install; auxiliary installation steps
have been integrated into the `postinstall` script.
* Updated developer docs `DEVELOPER.md` accordingly; also added
instructions to dev docs for performing full tests (via `npm test`) --
same as those run on Travis.
* Reorg in tests so that JS tests can run without a Dart env.
Partly fixes#945 **under the assumption that when running JS tests
locally, `ChromeCanary` is the desired browser to use**. Note that CI
tests (Travis) still uses `DartiumWithWebPlatform` across the board
(Maybe because ChromeCanary isn't being installed?)
Fixes#1012.
Closes#1010
Jeff Cross
Alex Eagle
Patrice Chalin
Yegor Jbanov