Revert "Use interceptors for is-checks (version 2)."

pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
index e5cd0e658130e8b395f26b7fd9cbe0946b123411..8adf3a9171e3a46432e915c49a531b6d1b8fd60c 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
@@ -641,12 +641,6 @@ class Builder implements cps_ir.Visitor/*<NodeCallback|Node>*/ {
     return new TypeOperator(value, node.dartType, typeArgs, isTypeTest: true);
   }
 
-  Expression visitTypeTestViaFlag(cps_ir.TypeTestViaFlag node) {
-    Expression value = getVariableUse(node.interceptor);
-    // TODO(sra): Move !! to cps_ir level.
-    return new Not(new Not(new GetTypeTestProperty(value, node.dartType)));
-  }
-
   Expression visitGetStatic(cps_ir.GetStatic node) {
     return new GetStatic(node.element, node.sourceInformation);
   }
@@ -706,3 +700,4 @@ class Builder implements cps_ir.Visitor/*<NodeCallback|Node>*/ {
   visitContinuation(cps_ir.Continuation node) => unexpectedNode(node);
   visitMutableVariable(cps_ir.MutableVariable node) => unexpectedNode(node);
 }
+