Change interfaces to abstract classes in dart2js compiler.

Change interfaces to abstract classes in dart2js compiler.

There are still a few interfaces left. They use the 'default implementation'
feature that can't be replaced until we implement const constructor forwarding.

Also removed mockimpl.dart. We don't pretend to support ReceiverPortFactory
(whatever it is) if it is not in the core library.

Committed: https://code.google.com/p/dart/source/detail?r=12252

[ngeoffray, 2012-09-12 09:30:56]

STV!

https://chromiumcodereview.appspot.com/10917208/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/builder.dart (right):

https://chromiumcodereview.appspot.com/10917208/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/builder.dart:713: factory JumpHandler(SsaBuilder
builder, TargetElement target) {
You know that this won't be valid after we switch to the new spec, right?

[Lasse Reichstein Nielsen, 2012-09-12 10:17:46]

https://chromiumcodereview.appspot.com/10917208/diff/1/lib/compiler/implement...
File lib/compiler/implementation/ssa/builder.dart (right):

https://chromiumcodereview.appspot.com/10917208/diff/1/lib/compiler/implement...
lib/compiler/implementation/ssa/builder.dart:713: factory JumpHandler(SsaBuilder
builder, TargetElement target) {
I think it'll still be valid. We still need normal factory methods, and not
forwarding constructors (that may or may not be generative for the class they
forward to).