[dart2js] Minor cleanup of classes needed for rti computation.

Change-Id: I641ed8f7c91f8b0d52b4542559a13b60d82e42e8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/205244
Commit-Queue: Joshua Litt <joshualitt@google.com>
Reviewed-by: Mayank Patke <fishythefish@google.com>

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

@@ -79,9 +79,6 @@ class CodeEmitterTask extends CompilerTask {
     // 'is$' method.
     typeTestRegistry.computeRequiredTypeChecks(
         _backendStrategy.rtiChecksBuilder, codegenWorld);
-    // Compute the classes needed by RTI.
-    typeTestRegistry.computeRtiNeededClasses(
-        codegen.rtiSubstitutions, _backendStrategy.generatedCode.keys);
   }
 
   /// Creates the [Emitter] for this task.
@@ -104,8 +101,7 @@ class CodeEmitterTask extends CompilerTask {
           _generateSourceMap);
       metadataCollector = new MetadataCollector(
           _compiler.reporter, _emitter, codegen.rtiRecipeEncoder);
-      typeTestRegistry = new TypeTestRegistry(
-          _compiler.options, closedWorld.elementEnvironment);
+      typeTestRegistry = new TypeTestRegistry(_compiler.options);
     });
   }
 

pkg/compiler/lib/src/js_emitter/program_builder/collector.dart

@@ -175,9 +175,7 @@ class Collector {
     // 4. Find all class types needed for rti.
     for (ClassEntity cls in _rtiNeededClasses) {
       if (backendTypeHelpers.contains(cls)) continue;
-      while (cls != null && neededClassTypes.add(cls)) {
-        cls = _elementEnvironment.getSuperClass(cls);
-      }
+      neededClassTypes.add(cls);
     }
 
     // 5. Sort classes and add them to their respective OutputUnits.

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

@@ -5,27 +5,20 @@
 library dart2js.js_emitter.type_test_registry;
 
 import '../common.dart';
-import '../common_elements.dart';
 import '../elements/entities.dart';
 import '../js_backend/runtime_types.dart'
     show RuntimeTypesChecks, RuntimeTypesChecksBuilder;
-import '../js_backend/runtime_types_codegen.dart'
-    show RuntimeTypesSubstitutions;
 import '../options.dart';
 import '../universe/codegen_world_builder.dart';
 
+/// TODO(joshualitt): Delete this class and store [RuntimeTypeChecks] on
+/// [CodeEmitterTask] directly.
 class TypeTestRegistry {
-  final ElementEnvironment _elementEnvironment;
-
-  /// After [computeNeededClasses] this set only contains classes that are only
-  /// used for RTI.
-  Set<ClassEntity> _rtiNeededClasses;
-
   final CompilerOptions _options;
 
   RuntimeTypesChecks _rtiChecks;
 
-  TypeTestRegistry(this._options, this._elementEnvironment);
+  TypeTestRegistry(this._options);
 
   RuntimeTypesChecks get rtiChecks {
     assert(
@@ -36,35 +29,7 @@ class TypeTestRegistry {
   }
 
   Iterable<ClassEntity> get rtiNeededClasses {
-    assert(
-        _rtiNeededClasses != null,
-        failedAt(NO_LOCATION_SPANNABLE,
-            "rtiNeededClasses has not been computed yet."));
-    return _rtiNeededClasses;
-  }
-
-  void computeRtiNeededClasses(RuntimeTypesSubstitutions rtiSubstitutions,
-      Iterable<MemberEntity> liveMembers) {
-    _rtiNeededClasses = new Set<ClassEntity>();
-
-    void addClassWithSuperclasses(ClassEntity cls) {
-      _rtiNeededClasses.add(cls);
-      for (ClassEntity superclass = _elementEnvironment.getSuperClass(cls);
-          superclass != null;
-          superclass = _elementEnvironment.getSuperClass(superclass)) {
-        _rtiNeededClasses.add(superclass);
-      }
-    }
-
-    void addClassesWithSuperclasses(Iterable<ClassEntity> classes) {
-      for (ClassEntity cls in classes) {
-        addClassWithSuperclasses(cls);
-      }
-    }
-
-    // Add classes that are referenced by type arguments or substitutions in
-    // argument checks.
-    addClassesWithSuperclasses(rtiChecks.requiredClasses);
+    return rtiChecks.requiredClasses;
   }
 
   void computeRequiredTypeChecks(