Remove support for script tags.

sdk/lib/_internal/compiler/implementation/ssa/builder.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 /**
  * A special element for the extra parameter taken by intercepted
  * methods. We need to override [Element.computeType] because our
  * optimizers may look at its declared type.
@@ skipping 5058 matching lines @@
     enterBlock.setBlockFlow(
         new HTryBlockInformation(
           wrapStatementGraph(bodyGraph),
           exception,
           wrapStatementGraph(catchGraph),
           wrapStatementGraph(finallyGraph)),
         exitBlock);
     inTryStatement = oldInTryStatement;
   }
 
-  visitScriptTag(ScriptTag node) {
-    compiler.unimplemented('SsaBuilder.visitScriptTag', node: node);
-  }
-
   visitCatchBlock(CatchBlock node) {
     visit(node.block);
   }
 
   visitTypedef(Typedef node) {
     compiler.unimplemented('SsaBuilder.visitTypedef', node: node);
   }
 
   visitTypeVariable(TypeVariable node) {
     compiler.internalError('SsaBuilder.visitTypeVariable');
@@ skipping 412 matching lines @@
           new HSubGraphBlockInformation(elseBranch.graph));
 
     HBasicBlock conditionStartBlock = conditionBranch.block;
     conditionStartBlock.setBlockFlow(info, joinBlock);
     SubGraph conditionGraph = conditionBranch.graph;
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }