Handle fuzzy optional parameters correctly.

Handle fuzzy optional parameters correctly.  Fixes
https://github.com/dart-lang/sdk/issues/26156 .

Adds translation of known function types in error_verifier.dart to
remove uses of dynamic before checking assignability.

BUG=
R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/56ab7bc39a00afeb9d75eb42b931710ca7b451be

[Leaf, 2016-04-15 23:52:26]

leafp@google.com changed reviewers:
+ brianwilkerson@google.com

[Leaf, 2016-04-15 23:52:26]

The least upper bound changes in type system are just from sorting the file -
sorry, must have forgotten to sort when I checked that in.  This fixes the
concrete bug mentioned, and is another step towards integrating the checker into
the error_verifier.

[Brian Wilkerson, 2016-04-16 00:01:14]

lgtm

[Leaf, 2016-04-16 00:31:26]

Description was changed from

==========
Handle fuzzy optional parameters correctly.  Fixes
https://github.com/dart-lang/sdk/issues/26156 .

Adds translation of known function types in error_verifier.dart to
remove uses of dynamic before checking assignability.

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

to

==========
Handle fuzzy optional parameters correctly.  Fixes
https://github.com/dart-lang/sdk/issues/26156 .

Adds translation of known function types in error_verifier.dart to
remove uses of dynamic before checking assignability.

BUG=
R=brianwilkerson@google.com

Committed:
https://github.com/dart-lang/sdk/commit/56ab7bc39a00afeb9d75eb42b931710ca7b451be
==========

[Leaf, 2016-04-16 00:31:27]

Committed patchset #1 (id:1) manually as
56ab7bc39a00afeb9d75eb42b931710ca7b451be (presubmit successful).