Collect the types used in is-checks in the resolver phase.

lib/compiler/implementation/compiler.dart

Index: lib/compiler/implementation/compiler.dart
diff --git a/lib/compiler/implementation/compiler.dart b/lib/compiler/implementation/compiler.dart
index 1b68df8719f13412a70e87a49c951672b67cbc8f..c8d62eab52bf38ee5c8f93701b9a4e39ab7144fe 100644
--- a/lib/compiler/implementation/compiler.dart
+++ b/lib/compiler/implementation/compiler.dart
@@ -371,9 +371,6 @@ class Compiler implements DiagnosticListener {
     assertMethod = coreLibrary.find(const SourceString('assert'));
 
     initializeSpecialClasses();
-
-    //patchDartLibrary(coreLibrary, 'core');
-    //patchDartLibrary(coreImplLibrary, 'coreimpl');
   }
 
   void importCoreLibrary(LibraryElement library) {
@@ -576,6 +573,11 @@ class Compiler implements DiagnosticListener {
 
     if (compilationFailed) return;
 
+    // TODO(karlklose): also take the instantiated types into account and move
+    // this computation to before codegen.
+    enqueuer.codegen.universe.computeRequiredTypes(
+        enqueuer.resolution.universe.isChecks);
+
     backend.assembleProgram();
 
     checkQueues();