Revert "Improvements to the kernel tree shaker."

pkg/kernel/lib/class_hierarchy.dart

Index: pkg/kernel/lib/class_hierarchy.dart
diff --git a/pkg/kernel/lib/class_hierarchy.dart b/pkg/kernel/lib/class_hierarchy.dart
index 40bc6e7972d429d37d03430eef3af6082b8cfc0b..6771cc4560220bc7865d7eaea80b2189e215927f 100644
--- a/pkg/kernel/lib/class_hierarchy.dart
+++ b/pkg/kernel/lib/class_hierarchy.dart
@@ -234,18 +234,11 @@ class ClassHierarchy {
 
   /// True if the program contains another class that is a subtype of given one.
   bool hasProperSubtypes(Class class_) {
-    // If there are no subtypes then the subtype set contains the class itself.
-    return !getSubtypesOf(class_).isSingleton;
-  }
-
-  /// Returns the subtypes of [class_] as an interval list.
-  ClassSet getSubtypesOf(Class class_) {
-    return new ClassSet(this, _infoFor[class_].subtypeIntervalList);
-  }
-
-  /// Returns the subclasses of [class_] as an interval list.
-  ClassSet getSubclassesOf(Class class_) {
-    return new ClassSet(this, _infoFor[class_].subclassIntervalList);
+    var info = _infoFor[class_];
+    var subtypes = info.subtypeIntervalList;
+    return !(subtypes.length == 2 &&
+        subtypes[0] == info.topDownIndex &&
+        subtypes[1] == info.topDownIndex + 1);
   }
 
   ClassHierarchy._internal(Program program, int numberOfClasses)
@@ -871,32 +864,3 @@ class _ClassInfo {
 
   _ClassInfo(this.classNode);
 }
-
-/// An immutable set of classes, internally represented as an interval list.
-class ClassSet {
-  final ClassHierarchy _hierarchy;
-  final Uint32List _intervalList;
-
-  ClassSet(this._hierarchy, this._intervalList);
-
-  bool get isEmpty => _intervalList.isEmpty;
-
-  bool get isSingleton {
-    var list = _intervalList;
-    return list.length == 2 && list[0] + 1 == list[1];
-  }
-
-  bool contains(Class class_) {
-    return _intervalListContains(
-        _intervalList, _hierarchy._infoFor[class_].topDownIndex);
-  }
-
-  ClassSet union(ClassSet other) {
-    assert(_hierarchy == other._hierarchy);
-    if (identical(_intervalList, other._intervalList)) return this;
-    _IntervalListBuilder builder = new _IntervalListBuilder();
-    builder.addIntervalList(_intervalList);
-    builder.addIntervalList(other._intervalList);
-    return new ClassSet(_hierarchy, builder.buildIntervalList());
-  }
-}