Clean up constructors for ScopedVisitor and derived classes.

Clean up constructors for ScopedVisitor and derived classes.

Previously, the classes ScopedVisitor, ResolverVisitor,
TypeResolverVisitor, and VariableResolverVisitor each had 4
independently maintained constructors, used respectively by
LibraryResolver (and DDC), the task model, the incremental resolver,
and LibraryResolver2.  This was difficult to maintain, and it was
about to get worse with the introduction of diet resolution.

This CL merges the constructors into one, using named optional
parameters where possible to reduce the burden on callers.

A few of the old constructors are kept on a temporary basis because
they are used by DDC, but they are deprecated; these can be removed
once DDC resolution is fully integrated with analyzer.

R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/cf790b08295a0dada006c61697f3854db3377893

[Paul Berry, 2015-06-30 22:01:21]

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

[Brian Wilkerson, 2015-06-30 22:06:31]

LGTM

[Paul Berry, 2015-06-30 22:37:22]

Committed patchset #2 (id:20001) manually as
cf790b08295a0dada006c61697f3854db3377893 (presubmit successful).