Fix some editor warnings.

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 1245 matching lines @@
     compiler.internalError('visitTry should not be called', instruction: node);
   }
 
   bool isEmptyElse(HBasicBlock start, HBasicBlock end) {
     if (start !== end) return false;
     if (start.last is !HGoto
         || start.last is HBreak
         || start.last is HContinue) {
       return false;
     }
-    HInstruction instruction = start.first;
     for (HInstruction instruction = start.first;
          instruction != start.last;
          instruction = instruction.next) {
       // Instructions generated at use site are okay because they do
       // not generate code in this else block.
       if (!isGenerateAtUseSite(instruction)) return false;
     }
     CopyHandler handler = variableNames.getCopyHandler(start);
     if (handler == null || handler.isEmpty()) return true;
     if (!handler.assignments.isEmpty()) return false;
@@ skipping 1228 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
     if (labeledBlockInfo.body.start.hasGuards()) {
       endBailoutSwitch();
     }
   }
 }