Fix 56 hints in pkg/compiler

pkg/compiler/lib/src/js_backend/patch_resolver.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.js_backend.patch_resolver;
 
 import '../dart2jslib.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../elements/modelx.dart';
@@ skipping 76 matching lines @@
               MessageKind.PATCH_POINT_TO_PARAMETER,
               {'parameterName': patchParameter.name});
         }
       }
     }
   }
 
   void checkMatchingPatchSignatures(FunctionElement origin,
                                     FunctionElement patch) {
     // TODO(johnniwinther): Show both origin and patch locations on errors.
-    FunctionExpression originTree = origin.node;
     FunctionSignature originSignature = origin.functionSignature;
     FunctionExpression patchTree = patch.node;
     FunctionSignature patchSignature = patch.functionSignature;
 
     if (originSignature.type.returnType != patchSignature.type.returnType) {
       compiler.withCurrentElement(patch, () {
         Node errorNode =
             patchTree.returnType != null ? patchTree.returnType : patchTree;
         compiler.reportError(
             errorNode, MessageKind.PATCH_RETURN_TYPE_MISMATCH,
@@ skipping 39 matching lines @@
              'originParameterCount': originSignature.optionalParameterCount,
              'patchParameterCount': patchSignature.optionalParameterCount});
       });
     } else {
       checkMatchingPatchParameters(origin,
                                    originSignature.optionalParameters,
                                    patchSignature.optionalParameters);
     }
   }
 
-}
+}