Finish strong mode cleaning of dart2js.

pkg/compiler/lib/src/js_emitter/full_emitter/emitter.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_emitter.full_emitter;
 
 import 'dart:collection' show HashMap;
 import 'dart:convert';
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
@@ skipping 1047 matching lines @@
 
         return false;
       })();
     ''');
 
     return supportsDirectProtoAccess;
   }
 
   jsAst.Expression generateLibraryDescriptor(
       LibraryEntity library, Fragment fragment) {
-    var uri = "";
+    dynamic uri = "";
     if (!compiler.options.enableMinification ||
         backend.mirrorsData.mustPreserveUris) {
       uri = library.canonicalUri;
       if (uri.scheme == 'file' && compiler.options.outputUri != null) {
         uri =
             relativize(compiler.options.outputUri, library.canonicalUri, false);
       }
     }
 
     String libraryName = (!compiler.options.enableMinification ||
@@ skipping 542 matching lines @@
     return outputs;
   }
 
   void finalizeTokensInAst(
       jsAst.Program main, Iterable<jsAst.Program> deferredParts) {
     jsAst.TokenCounter counter = new jsAst.TokenCounter();
     counter.countTokens(main);
     deferredParts.forEach(counter.countTokens);
     task.metadataCollector.finalizeTokens();
     if (backend.namer is jsAst.TokenFinalizer) {
-      var finalizer = backend.namer;
+      dynamic finalizer = backend.namer;
       finalizer.finalizeTokens();
     }
   }
 
   int emitProgram(ProgramBuilder programBuilder) {
     Program program =
         programBuilder.buildProgram(storeFunctionTypesInMetadata: true);
 
     outputStaticNonFinalFieldLists =
         programBuilder.collector.outputStaticNonFinalFieldLists;
@@ skipping 330 matching lines @@
     // data.
     mapping["_comment"] = "This mapping shows which compiled `.js` files are "
         "needed for a given deferred library import.";
     mapping.addAll(compiler.deferredLoadTask.computeDeferredMap());
     compiler.outputProvider(
         compiler.options.deferredMapUri.path, '', OutputType.info)
       ..add(const JsonEncoder.withIndent("  ").convert(mapping))
       ..close();
   }
 }