Warnings in observatory build

[karlklose]

Running build.py shows the following warnings when building observatory:

[Warning from polymer (PolymerBootstrapTransformer) on observatory|web/index.html]:
We have detected a cycle in your import graph when running initializers on ActionLinkElement. This means the super class ObservatoryElement has a dependency on this library (possibly transitive).
[Warning from polymer (PolymerBootstrapTransformer) on observatory|web/index.html]:
We have detected a cycle in your import graph when running initializers on LibraryRefElement. This means the super class ServiceRefElement has a dependency on this library (possibly transitive).
[Info from Dart2JS]:
Compiling observatory|web/index.html.polymer.bootstrap.dart...
[Warning from Dart2JS on observatory|web/index.html.polymer.bootstrap.dart]:
packages/charted/selection/src/transition_impl.dart:145:32:
The element type 'Map' of 'List<Map>' is not assignable to 'Interpolator'.
    for (Interpolator tween in _attrMap[activeNode]) {
                               ^^^^^^^^^^^^^^^^^^^^
[Warning from Dart2JS on observatory|web/index.html.polymer.bootstrap.dart]:
packages/charted/core/utils/color.dart:279:26:
No member named 'iterator' in class 'String'.
      for (final char in hex) {
                         ^^^

There should be no warnings.

[johnmccutchan]

Blocked by google/charted#167

[johnmccutchan]

@B3rn475 Can you please try updating the charted package to 0.4.x to see if this has gone away?