Fix 56 hints in pkg/compiler

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

Index: pkg/compiler/lib/src/js_backend/patch_resolver.dart
diff --git a/pkg/compiler/lib/src/js_backend/patch_resolver.dart b/pkg/compiler/lib/src/js_backend/patch_resolver.dart
index 56c5203c07e81d096e4145710b4d5913aa7892d4..34a501438758ca7b4caf02105254fd4c99639738 100644
--- a/pkg/compiler/lib/src/js_backend/patch_resolver.dart
+++ b/pkg/compiler/lib/src/js_backend/patch_resolver.dart
@@ -94,7 +94,6 @@ class PatchResolverTask extends CompilerTask {
   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;
@@ -154,4 +153,4 @@ class PatchResolverTask extends CompilerTask {
     }
   }
 
-}
+}