dart2js: Recanonicalize selectors in static fields between runs.

dart2js: Recanonicalize selectors in static fields between runs.

This fixes a bug in batch-mode.

Selectors are canonicalized upon construction, so two equal selectors
are always the same object.

To avoid memory leaks in batch mode, the compiler clears the canonical
cache before each run.

However, some selectors were stored in static fields and thus shared
between runs.  These selectors lost their canonical status when the
cache was cleared.  This patch "fixes" that by reinserting them in
the cache after clearing it.

BUG=
R=johnniwinther@google.com

Committed: https://github.com/dart-lang/sdk/commit/392bed583cce5470913d378d1f7577cfd7d83974

[asgerf, 2015-11-18 12:00:58]

Description was changed from

==========
dart2js: Recanonicalize selectors in static fields between runs.

Selectors are canonicalized upon construction, so two equal selectors
are always the same object.

To avoid memory leaks in batch mode, the compiler clears the canonical
cache before each run.

However, some selectors were stored in static fields and thus shared
between runs.  These selectors lost their canonical status when the
cache was cleared.  This patch "fixes" that by reinserting them in
the cache after clearing it.

BUG=
==========

to

==========
dart2js: Recanonicalize selectors in static fields between runs.

This fixes a bug in batch-mode.

Selectors are canonicalized upon construction, so two equal selectors
are always the same object.

To avoid memory leaks in batch mode, the compiler clears the canonical
cache before each run.

However, some selectors were stored in static fields and thus shared
between runs.  These selectors lost their canonical status when the
cache was cleared.  This patch "fixes" that by reinserting them in
the cache after clearing it.

BUG=
==========

[asgerf, 2015-11-18 12:16:39]

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

[Johnni Winther, 2015-11-18 12:45:54]

lgtm

[asgerf, 2015-11-18 12:55:20]

Committed patchset #1 (id:1) manually as
392bed583cce5470913d378d1f7577cfd7d83974 (presubmit successful).