Propertly summarize LUB function types.

Propertly summarize LUB function types.

When a function type arises out of a LUB (least upper bound)
computation, it pionts to a synthetic FunctionElement that is not
connected to the element model, so we can't summarize it by simply
storing a reference to the FunctionElement.  We have to store the
FunctionElement's return type and type parameters.

This required reworking _CompilationUnitSerializer's mechanism for
tracking whether it is creating linked or unlinked references;
previously it kept track by passing a boolean around.  Now it uses a
bool field, which should be much less error prone.

Fixes generation of strong mode SDK summary (previously it failed with
an assertion error when in checked mode).

R=scheglov@google.com

Committed: https://github.com/dart-lang/sdk/commit/293267db28642cb235522064983b3921dca872c1

[Paul Berry, 2016-02-26 00:11:27]

paulberry@google.com changed reviewers:
+ scheglov@google.com

[scheglov, 2016-02-26 05:12:01]

LGTM

[Paul Berry, 2016-02-26 16:28:25]

Description was changed from

==========
Propertly summarize LUB function types.

When a function type arises out of a LUB (least upper bound)
computation, it pionts to a synthetic FunctionElement that is not
connected to the element model, so we can't summarize it by simply
storing a reference to the FunctionElement.  We have to store the
FunctionElement's return type and type parameters.

This required reworking _CompilationUnitSerializer's mechanism for
tracking whether it is creating linked or unlinked references;
previously it kept track by passing a boolean around.  Now it uses a
bool field, which should be much less error prone.

Fixes generation of strong mode SDK summary (previously it failed with
an assertion error when in checked mode).
==========

to

==========
Propertly summarize LUB function types.

When a function type arises out of a LUB (least upper bound)
computation, it pionts to a synthetic FunctionElement that is not
connected to the element model, so we can't summarize it by simply
storing a reference to the FunctionElement.  We have to store the
FunctionElement's return type and type parameters.

This required reworking _CompilationUnitSerializer's mechanism for
tracking whether it is creating linked or unlinked references;
previously it kept track by passing a boolean around.  Now it uses a
bool field, which should be much less error prone.

Fixes generation of strong mode SDK summary (previously it failed with
an assertion error when in checked mode).

R=scheglov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/293267db28642cb235522064983b3921dca872c1
==========

[Paul Berry, 2016-02-26 16:28:26]

Committed patchset #1 (id:1) manually as
293267db28642cb235522064983b3921dca872c1 (presubmit successful).