Avoid repeated declaration of the same loop variable.

lib/compiler/implementation/ssa/codegen.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.
 
 class SsaCodeGeneratorTask extends CompilerTask {
   final JavaScriptBackend backend;
   SsaCodeGeneratorTask(JavaScriptBackend backend)
       : this.backend = backend,
         super(backend.compiler);
   String get name() => 'SSA code generator';
@@ skipping 450 matching lines @@
   }
 
   void declareVariable(String variableName) {
     if (isGeneratingExpression()) {
       if (generationState == STATE_FIRST_DECLARATION) {
         generationState = STATE_DECLARATION;
         if (!isVariableDeclared(variableName)) {
           declaredVariables.add(variableName);
           buffer.add("var ");
         }
-      } else if (!isGeneratingDeclaration()
-                 && !isVariableDeclared(variableName)) {
-        delayedVariablesDeclaration.add(variableName);
+      } else if (!isVariableDeclared(variableName)) {
+        if (!isGeneratingDeclaration()) {
+          delayedVariablesDeclaration.add(variableName);
+        } else {
+          declaredVariables.add(variableName);
+        }
       }
     } else if (!isVariableDeclared(variableName)) {
       declaredVariables.add(variableName);
       buffer.add("var ");
     }
     buffer.add(variableName);
   }
 
   void declareInstruction(HInstruction instruction) {
     declareVariable(variableNames.getName(instruction));
@@ skipping 2011 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
     if (labeledBlockInfo.body.start.hasGuards()) {
       endBailoutSwitch();
     }
   }
 }