Roll Observatory deps (charted -> ^0.3.0)

I had to restrict both the analyzer and dart_style to old versions to
get the build to work :-/.  Otherwise I got errors like this:

    Transform polymer (PolymerBootstrapTransformer) on
    observatory|web/index.html threw error: Class 'Parser' has no
    instance setter 'parseConditionalDirectives='.

Added missing exclude to pubspec.yaml.

BUG=

Review URL: https://codereview.chromium.org//1521693002 .
350 files changed
tree: 25fb55d1396e005651447d20f1c702a24b9f1d95
  1. packages/
  2. codereview.settings
  3. pubspec.yaml
  4. README.md
  5. roll.py
README.md

Snapshot of Observatory pub package dependencies needed to build

The pubspec.yaml in this repository is the source of truth