Extract DartTypeVisitor and subclasses from resolution_types.

pkg/compiler/lib/src/js_backend/runtime_types.dart

Index: pkg/compiler/lib/src/js_backend/runtime_types.dart
diff --git a/pkg/compiler/lib/src/js_backend/runtime_types.dart b/pkg/compiler/lib/src/js_backend/runtime_types.dart
index a9cf0ba1cb6b664cdf264d4369b61a57d169700a..e6dd1f7a8c956e4a5d3fb376242f99998a002aa8 100644
--- a/pkg/compiler/lib/src/js_backend/runtime_types.dart
+++ b/pkg/compiler/lib/src/js_backend/runtime_types.dart
@@ -852,7 +852,7 @@ class _RuntimeTypesEncoder implements RuntimeTypesEncoder {
   }
 }
 
-class TypeRepresentationGenerator implements DartTypeVisitor {
+class TypeRepresentationGenerator implements ResolutionDartTypeVisitor {
   final Namer namer;
   OnVariableCallback onVariable;
   ShouldEncodeTypedefCallback shouldEncodeTypedef;
@@ -1072,7 +1072,7 @@ class TypeCheckMapping implements TypeChecks {
   }
 }
 
-class ArgumentCollector extends DartTypeVisitor {
+class ArgumentCollector extends ResolutionDartTypeVisitor {
   final Set<ClassElement> classes = new Set<ClassElement>();
 
   collect(ResolutionDartType type, {bool isTypeArgument: false}) {
@@ -1101,7 +1101,7 @@ class ArgumentCollector extends DartTypeVisitor {
   }
 }
 
-class FunctionArgumentCollector extends DartTypeVisitor {
+class FunctionArgumentCollector extends ResolutionDartTypeVisitor {
   final Set<ClassElement> classes = new Set<ClassElement>();
 
   FunctionArgumentCollector();