dart2js cps: Make Identical a built-in and add Interceptor to Tree IR.

dart2js cps: Make Identical a built-in and add Interceptor to Tree IR.

Identical is now a built-in operator instead of a separate primitive.

Interceptor is now its own expression in the Tree IR instead of a static
invocation. This matches the CPS IR (where it is a primitive), and
should fix a problem it was causing for frequency-based naming.

The JS-specific subclass of the Tree IR builder no longer depended on
the backend, emitter, namer, glue, compiler, or anything so it has
been merged into the superclass.

BUG=
R=kmillikin@google.com

Committed: https://github.com/dart-lang/sdk/commit/05497633df4c27dcbd99a9e942e9153d196f9673

[asgerf, 2015-06-23 13:25:40]

asgerf@google.com changed reviewers:
+ kmillikin@google.com

[asgerf, 2015-06-23 13:25:40]

https://codereview.chromium.org/1204733002/diff/1/pkg/compiler/lib/src/cps_ir...
File pkg/compiler/lib/src/cps_ir/type_propagation.dart (left):

https://codereview.chromium.org/1204733002/diff/1/pkg/compiler/lib/src/cps_ir...
pkg/compiler/lib/src/cps_ir/type_propagation.dart:572: if (use is Identical &&
use.hasNoUses) continue;
Now that unused primitives are not no-ops, it's just not practical to check this
here. Unused primitives are removed eagerly instead.

[Kevin Millikin (Google), 2015-06-23 13:43:04]

LGTM.

[asgerf, 2015-06-23 14:04:02]

Committed patchset #1 (id:1) manually as
05497633df4c27dcbd99a9e942e9153d196f9673 (presubmit successful).