Split _LibrarySerializer into two classes.

Split _LibrarySerializer into two classes.

The new class, _CompilationUnitSerializer, is responsible for
serializing a single compilation unit.  In a future CL, this will allow
us to serialize all the compilation units for a given library in phases,
retaining state information in each of the _CompilationUnitSerializers.

Also, this fixes a previously undiscovered bug where we were trying to
use the same reference index to represent unresolved references across
compilation units; the correct behavior is for each compilation unit to
have its own index for unresolved references.

R=scheglov@google.com

Committed: https://github.com/dart-lang/sdk/commit/738b835b0b62578327714558c17c5b631588f602

[Paul Berry, 2016-01-20 04:47:43]

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

[scheglov, 2016-01-20 04:52:55]

LGTM

[Paul Berry, 2016-01-20 05:09:57]

Description was changed from

==========
Split _LibrarySerializer into two classes.

The new class, _CompilationUnitSerializer, is responsible for
serializing a single compilation unit.  In a future CL, this will allow
us to serialize all the compilation units for a given library in phases,
retaining state information in each of the _CompilationUnitSerializers.

Also, this fixes a previously undiscovered bug where we were trying to
use the same reference index to represent unresolved references across
compilation units; the correct behavior is for each compilation unit to
have its own index for unresolved references.
==========

to

==========
Split _LibrarySerializer into two classes.

The new class, _CompilationUnitSerializer, is responsible for
serializing a single compilation unit.  In a future CL, this will allow
us to serialize all the compilation units for a given library in phases,
retaining state information in each of the _CompilationUnitSerializers.

Also, this fixes a previously undiscovered bug where we were trying to
use the same reference index to represent unresolved references across
compilation units; the correct behavior is for each compilation unit to
have its own index for unresolved references.

R=scheglov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/738b835b0b62578327714558c17c5b631588f602
==========

[Paul Berry, 2016-01-20 05:09:58]

Committed patchset #1 (id:1) manually as
738b835b0b62578327714558c17c5b631588f602 (presubmit successful).