- The flow graph builder is only used to visit Statements and
Expressions so it does not need TreeVisitor as a base class. This
will make refactoring it easier.
- The TranslationHelper is bound to a Thread so we do not need
Thread::Current where we have a TranslationHelper.
- BlockExpression does not exist in Kernel any more, so it can be
removed from the C++ AST implementation.
BUG=
R=kustermann@google.com
Review-Url: https://codereview.chromium.org/2624513005 .