Redo "Steps towards making dart2js JS AST templates an indepentent library."

pkg/compiler/lib/src/js/rewrite_async.dart

Index: pkg/compiler/lib/src/js/rewrite_async.dart
diff --git a/pkg/compiler/lib/src/js/rewrite_async.dart b/pkg/compiler/lib/src/js/rewrite_async.dart
index 3f5bfaa967a14477c4b53910e173539cbdd9f2ed..656b1af9d9bdff50e11d41d8c8b1ef0961d644d1 100644
--- a/pkg/compiler/lib/src/js/rewrite_async.dart
+++ b/pkg/compiler/lib/src/js/rewrite_async.dart
@@ -966,11 +966,6 @@ class AsyncRewriter extends js.NodeVisitor {
   }
 
   @override
-  js.Expression visitBlob(js.Blob node) {
-    return node;
-  }
-
-  @override
   void visitBlock(js.Block node) {
     for (js.Statement statement in node.statements) {
       visitStatement(statement);
@@ -1822,11 +1817,6 @@ class PreTranslationAnalysis extends js.NodeVisitor<bool> {
   }
 
   @override
-  bool visitBlob(js.Blob node) {
-    return false;
-  }
-
-  @override
   bool visitBlock(js.Block node) {
     bool containsAwait = false;
     for (js.Statement statement in node.statements) {