This CL creates top level accessor functions which may be used to map from AST data structures to their corresponding elements and types, and begins using those accessor functions throughout the SDK. It also adds empty interfaces ResolutionTarget and ResolutionType, which are implemented by Element and DartType respectively.
In a future CL, I will change the types stored in the AST to ResolutionTarget and ResolutionType, rather than specific element types; this will decouple the ASTs from the element model. The presence of the accessor functions will allow clients to continue accessing elements and types in a type-safe way.
R=asgerf@google.com, brianwilkerson@google.com, scheglov@google.com, vsm@google.com
Review URL: https://codereview.chromium.org/2551023005 .
Brian Wilkerson