Revert "Allow LetCont to bind multiple continuations."

pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart
index ce5fa00e184a2953a1580673fd860259a3d5720f..b292b4e5a40a78195b4123c7a8cf337637b7011d 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_visitor.dart
@@ -468,8 +468,7 @@ class IrBuilderVisitor extends ResolvedVisitor<ir.Primitive>
       });
       joinContinuation = new ir.Continuation(parameters);
       irBuilder.invokeFullJoin(joinContinuation, jumps, recursive: false);
-      irBuilder.add(new ir.LetCont(<ir.Continuation>[joinContinuation],
-          innerBuilder._root));
+      irBuilder.add(new ir.LetCont(joinContinuation, innerBuilder._root));
       for (int i = 0; i < irBuilder.environment.length; ++i) {
         irBuilder.environment.index2value[i] = parameters[i];
       }
@@ -940,7 +939,7 @@ class IrBuilderVisitor extends ResolvedVisitor<ir.Primitive>
       ir.Continuation k = new ir.Continuation([valueToStore]);
       ir.Expression invoke =
           new ir.InvokeMethod(originalValue, operatorSelector, k, [arg]);
-      irBuilder.add(new ir.LetCont(<ir.Continuation>[k], invoke));
+      irBuilder.add(new ir.LetCont(k, invoke));
     }
 
     if (Elements.isLocal(element)) {