Transform constructor arguments correctly.

[jakemac53]

Currently, only things like @foo('bar') are supported. We should support passing other values as well, to support cases like:

String name = 'bar';
@foo(name)

[jakemac53]

From the code review:

Siggi Cherem (dart-lang) 2015/01/16 19:46:29
Note that we need to check whether or not we need to transform the arguments
too, for example, if you have:

a.dart:
const theName = 'x-foo';

b.dart:
@CustomTag(theName)
class XFoo {}

we need to import a.dart also to be able to refer to theName. This can get quite
complex if you have nested expressions and what not.

Now that I think more about it, I realized that smoke creates a table that
includes annotations, so we had to do it there. Here is the example output:
https://github.com/dart-lang/smoke/blob/master/test/static_test.dart#L83

And here is the logic we did for it:
https://github.com/dart-lang/smoke/blob/master/lib/codegen/recorder.dart#L247

Feel free to copy it, or maybe change smoke to make some of these helpers
public. The codegen/generator.dart file also has some useful bits, like the
CodeAsConstExpression and other bits that help generate code that use library
prefixes (see
https://github.com/dart-lang/smoke/blob/master/lib/codegen/generator.dart#L321)

[jakemac53]

https://codereview.chromium.org/865293002/ is out to fix this.