[js_ast] adds Identifier that merges VariableDeclaration/Use and Parameter

[js_ast] adds Identifier that merges VariableDeclaration/Use and Parameter

Also changes Printer to not walk the tree an extra time unless we are minifiying.

The tree structure appears to be helping VarCollector, by encoding some information into the static AST structure. (although some aspects were unused, such as function names). It's easy enough to encode this behavior in VarCollector itself. Having a unified Identifier benefits our tree transform, since we don't need to worry about generating three different types of things under largely identical circumstances.

I'm planning to build on this later, but this version is purely a refactor.

R=vsm@google.com

Committed: https://github.com/dart-lang/dev_compiler/commit/2ce12f647a20e8125bf1617a331f25f65a58d16d

[Jennifer Messerly, 2015-03-25 21:27:18]

jmesserly@google.com changed reviewers:
+ vsm@google.com

[Jennifer Messerly, 2015-03-25 21:29:17]

https://codereview.chromium.org/1029583011/diff/1/lib/src/js/printer.dart
File lib/src/js/printer.dart (left):

https://codereview.chromium.org/1029583011/diff/1/lib/src/js/printer.dart#old...
lib/src/js/printer.dart:1138: class OrderedSet<T> {
presumably this predates LinkedHashSet

https://codereview.chromium.org/1029583011/diff/1/lib/src/js/template.dart
File lib/src/js/template.dart (left):

https://codereview.chromium.org/1029583011/diff/1/lib/src/js/template.dart#ol...
lib/src/js/template.dart:184: assert(identiferRE.hasMatch(value));
this check already happens in the constructor

[vsm, 2015-03-25 22:46:01]

lgtm

[Jennifer Messerly, 2015-03-25 23:01:06]

Committed patchset #1 (id:1) manually as
2ce12f647a20e8125bf1617a331f25f65a58d16d (presubmit successful).