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

lib/compiler/implementation/ssa/builder.dart

Index: lib/compiler/implementation/ssa/builder.dart
diff --git a/lib/compiler/implementation/ssa/builder.dart b/lib/compiler/implementation/ssa/builder.dart
index a070e778a5e00a2ec189e6df97ad3b64be128bed..d804b64842a41d15ab83b7d96fd8b26204f2c06b 100644
--- a/lib/compiler/implementation/ssa/builder.dart
+++ b/lib/compiler/implementation/ssa/builder.dart
@@ -2610,7 +2610,7 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
     if (element != null && element.isErroneous()) {
       ErroneousElement error = element;
       Message message = error.errorMessage;
-      if (message.kind === MessageKind.CANNOT_FIND_CONSTRUCTOR) {
+      if (message.kind == MessageKind.CANNOT_FIND_CONSTRUCTOR) {
         Element helper =
             compiler.findHelper(const SourceString('throwNoSuchMethod'));
         DartString receiverLiteral = new DartString.literal('');
@@ -2627,7 +2627,7 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
         HInstruction arguments = new HLiteralList(inputs);
         add(arguments);
         pushInvokeHelper3(helper, receiver, name, arguments);
-      } else if (message.kind === MessageKind.CANNOT_RESOLVE) {
+      } else if (message.kind == MessageKind.CANNOT_RESOLVE) {
         generateRuntimeError(node.send, message.message);
       } else {
         compiler.internalError('unexpected unresolved constructor call',