Remove support for script tags.

sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart

Index: sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
index 4979d19abc4e02c33243e62fa339b2050dbfa1d4..61bad39d83a10315304b7bbd6c7b67e406cbb5d2 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
@@ -169,11 +169,6 @@ class CloningVisitor implements Visitor<Node> {
   visitReturn(Return node) => new Return(
       node.beginToken, node.endToken, visit(node.expression));
 
-  visitScriptTag(ScriptTag node) => new ScriptTag(
-      visit(node.tag), visit(node.argument),
-      visit(node.prefixIdentifier), visit(node.prefix),
-      node.beginToken, node.endToken);
-
   visitSend(Send node) => new Send(
       visit(node.receiver), visit(node.selector), visit(node.argumentsNode));