Use LibraryIndex in CoreTypes instead of extending it.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index ff6d4eb0013035c9182867770f0074c68f32a997..3253ef5aa4e786e81097b4f4843a4e5ba2fb6d25 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -612,8 +612,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   finishSend(Object receiver, Arguments arguments, int charOffset) {
     bool isIdentical(Object receiver) {
       return receiver is StaticAccessor &&
-          receiver.readTarget ==
-              coreTypes.tryGetTopLevelMember("dart:core", null, "identical");
+          receiver.readTarget == coreTypes.identicalProcedure;
     }
 
     if (receiver is FastaAccessor) {
@@ -784,7 +783,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     }
     warning(message, charOffset);
     Constructor constructor =
-        coreTypes.getClass("dart:core", "NoSuchMethodError").constructors.first;
+        coreTypes.noSuchMethodErrorClass.constructors.first;
     return new Throw(new ConstructorInvocation(
         constructor,
         astFactory.arguments(<Expression>[