dart2js: Rename old emitter to full emitter and make it its own library.

pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart

Index: pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart b/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
index 52c43524e04282b8b57ee36d64793c0bb1b08db9..b5e1a578ed926a70ee12fba49bca79123ce5a7ad 100644
--- a/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart
@@ -4,6 +4,12 @@
 
 part of dart2js.js_emitter;
 
+// Function signatures used in the generation of runtime type information.
+typedef void FunctionTypeSignatureEmitter(Element method,
+                                          FunctionType methodType);
+
+typedef void SubstitutionEmitter(Element element, {bool emitNull});
+
 class TypeTestProperties {
   /// The index of the function type into the metadata.
   ///