Remove ClassWorld.subclassesOf and ClassWorld.subtypesOf.

pkg/compiler/lib/src/types/type_mask.dart

Index: pkg/compiler/lib/src/types/type_mask.dart
diff --git a/pkg/compiler/lib/src/types/type_mask.dart b/pkg/compiler/lib/src/types/type_mask.dart
index 8e4e2d22ce07c0caceb80b7b93587592d33aaf27..bf095b860dbf609ef9cc5367f1a3cc661ad203ef 100644
--- a/pkg/compiler/lib/src/types/type_mask.dart
+++ b/pkg/compiler/lib/src/types/type_mask.dart
@@ -33,7 +33,7 @@ abstract class TypeMask {
   }
 
   factory TypeMask.subclass(ClassElement base, ClassWorld classWorld) {
-    if (classWorld.hasAnySubclass(base)) {
+    if (classWorld.hasAnyStrictSubclass(base)) {
       return new FlatTypeMask.subclass(base);
     } else {
       return new TypeMask.exactOrEmpty(base, classWorld);
@@ -44,7 +44,7 @@ abstract class TypeMask {
     if (classWorld.hasOnlySubclasses(base)) {
       return new TypeMask.subclass(base, classWorld);
     }
-    if (classWorld.hasAnySubtype(base)) {
+    if (classWorld.hasAnyStrictSubtype(base)) {
       return new FlatTypeMask.subtype(base);
     } else {
       return new TypeMask.exactOrEmpty(base, classWorld);
@@ -69,7 +69,7 @@ abstract class TypeMask {
   }
 
   factory TypeMask.nonNullSubclass(ClassElement base, ClassWorld classWorld) {
-    if (classWorld.hasAnySubclass(base)) {
+    if (classWorld.hasAnyStrictSubclass(base)) {
       return new FlatTypeMask.nonNullSubclass(base);
     } else {
       return new TypeMask.nonNullExactOrEmpty(base, classWorld);
@@ -80,7 +80,7 @@ abstract class TypeMask {
     if (classWorld.hasOnlySubclasses(base)) {
       return new TypeMask.nonNullSubclass(base, classWorld);
     }
-    if (classWorld.hasAnySubtype(base)) {
+    if (classWorld.hasAnyStrictSubtype(base)) {
       return new FlatTypeMask.nonNullSubtype(base);
     } else {
       return new TypeMask.nonNullExactOrEmpty(base, classWorld);
@@ -126,13 +126,13 @@ abstract class TypeMask {
         return null;
       }
       if (mask.isSubclass) {
-        if (!classWorld.hasAnySubclass(mask.base)) {
+        if (!classWorld.hasAnyStrictSubclass(mask.base)) {
           return 'Subclass ${mask.base} does not have any subclasses.';
         }
         return null;
       }
       assert(mask.isSubtype);
-      if (!classWorld.hasAnySubtype(mask.base)) {
+      if (!classWorld.hasAnyStrictSubtype(mask.base)) {
         return 'Subtype ${mask.base} does not have any subclasses.';
       }
       if (classWorld.hasOnlySubclasses(mask.base)) {