dart2js cps: Fix performance issues in optimization passes.

dart2js cps: Fix performance issues in optimization passes.

Type propagation, shrinking reductions, and let sinking each took
more than 2 minutes on a stress test, where now they take a few
seconds.

Huge hash tables (Map/Set) were a big problem, especially when used as
worklists.

Let sinking had an issue with a linear-time search for the enclosing
continuation of an expression. This has been replaced with a visitor
state.

The stress test was:

  tests/co19/src/LibTest/collection/ListBase/ListBase_class_A01_t02

This was only slow because negative constants get translated to
intercepted calls. That itself should be fixed, but the IR should
still be able to handle the stress.

The change in shrinking reductions altered the redex priority from
FIFO to LIFO which has a negative effect on code quality in
unwrapException (in any test case with a try/catch). It seems like
an existing issue that has surfaced.

Since I am going on vacation, I ask that someone would please
commit this on my behalf (assuming things are looking good).
--asgerf

BUG=
R=karlklose@google.com

Committed: https://github.com/dart-lang/sdk/commit/2a137d16dba4bf15f4d63322db179b1e78b56856

[asgerf, 2015-07-24 13:00:30]

asgerf@google.com changed reviewers:
+ floitsch@google.com, karlklose@google.com, kmillikin@google.com

[karlklose, 2015-07-27 08:44:06]

LGTM.

I will commit it for you.

[karlklose, 2015-07-27 10:12:11]

Committed patchset #2 (id:20001) manually as
2a137d16dba4bf15f4d63322db179b1e78b56856 (presubmit successful).