dart2js: Change typedef encoding.

dart2js: Change typedef encoding.

Currently typedefs have a descriptor field that looks like they don't have any super-class:

_Equality: {
  "^": ":58"
}

When we call finishClass we thus assume that it's the Dart Object class. While this didn't hurt (as far as I could tell), it feels wrong.

Since typedefs are only emitted when reflection is enabled I'm ok with adding more code to the output (not that it's that much).

The output now looks as follows:

  _Equality: {
    "^": "Object;",
    $typedefType: 58,
    $$isTypedef: true
  },


At the same time I removed the shared encoding class. It turns out that it doesn't give a lot of flexibility, and by using the shared embedded constant strings, the linkage is not too bad.

R=karlklose@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42437

[floitsch, 2014-12-17 00:23:49]

floitsch@google.com changed reviewers:
+ karlklose@google.com

[floitsch, 2014-12-17 00:23:49]

What is still missing: asserts that the added fields can't clash with other
properties. I checked and properties with a leading "$" should not clash, but we
should `assert(namer.isInternalName(X))` for all properties that we add
directly. (@zarah: hint).

[karlklose, 2014-12-17 09:33:15]

LGTM with a comment.

I still think that the version with the shared encoding/decoding was easier to
read and I would rather move more of the encoding/decoding into the shared
library or a builder. Also, the names of these functions documents what is
happening, so we should perhaps have a comment in the new code instead.

[floitsch, 2014-12-17 15:18:07]

Committed patchset #2 (id:20001) manually as 42437 (presubmit successful).