The new class becomes a superclass of CoreTypes, which now gets its
functionality from that class, but also exposes commonly used built-in
members as fields.
This replaces a couple of ad-hoc linear searches spread throughout
the code.
The canonical names are not a convenient interface for transformers, so
the idea is that they can use LibraryIndex to address their own runtime
libraries.
To avoid name clashes and still have a somewhat convenient interface,
getters and setters are prefixed by 'get:' and 'set:' in the lookup
table (and only in the lookup table), and top-level members can be
accessed using '::' as the class name. This is the same convention
used by the VM, although it is currently not required to be the same.
R=dmitryas@google.com, karlklose@google.com, kmillikin@google.com
Review-Url: https://codereview.chromium.org/2706243011 .
Peter von der Ahé