Use const for const/final top-levels, types, symbols.

lib/runtime/dart/_js_embedded_names.js

 dart_library.library('dart/_js_embedded_names', null, /* Imports */[
   "dart/_runtime"
 ], /* Lazy imports */[
 ], function(exports, dart) {
   'use strict';
   let dartx = dart.dartx;
-  let DISPATCH_PROPERTY_NAME = "dispatchPropertyName";
-  let TYPE_INFORMATION = 'typeInformation';
-  let GLOBAL_FUNCTIONS = 'globalFunctions';
-  let STATICS = 'statics';
-  let INTERCEPTED_NAMES = 'interceptedNames';
-  let MANGLED_GLOBAL_NAMES = 'mangledGlobalNames';
-  let MANGLED_NAMES = 'mangledNames';
-  let LIBRARIES = 'libraries';
-  let FINISHED_CLASSES = 'finishedClasses';
-  let ALL_CLASSES = 'allClasses';
-  let METADATA = 'metadata';
-  let INTERCEPTORS_BY_TAG = 'interceptorsByTag';
-  let LEAF_TAGS = 'leafTags';
-  let LAZIES = 'lazies';
-  let GET_ISOLATE_TAG = 'getIsolateTag';
-  let ISOLATE_TAG = 'isolateTag';
-  let CURRENT_SCRIPT = 'currentScript';
-  let DEFERRED_LIBRARY_URIS = 'deferredLibraryUris';
-  let DEFERRED_LIBRARY_HASHES = 'deferredLibraryHashes';
-  let INITIALIZE_LOADED_HUNK = 'initializeLoadedHunk';
-  let IS_HUNK_LOADED = 'isHunkLoaded';
-  let IS_HUNK_INITIALIZED = 'isHunkInitialized';
-  let DEFERRED_INITIALIZED = 'deferredInitialized';
-  let CLASS_ID_EXTRACTOR = 'classIdExtractor';
-  let CLASS_FIELDS_EXTRACTOR = 'classFieldsExtractor';
-  let INSTANCE_FROM_CLASS_ID = "instanceFromClassId";
-  let INITIALIZE_EMPTY_INSTANCE = "initializeEmptyInstance";
-  let TYPEDEF_TYPE_PROPERTY_NAME = "$typedefType";
-  let TYPEDEF_PREDICATE_PROPERTY_NAME = "$$isTypedef";
-  let NATIVE_SUPERCLASS_TAG_NAME = "$nativeSuperclassTag";
-  let MAP_TYPE_TO_INTERCEPTOR = "mapTypeToInterceptor";
+  const DISPATCH_PROPERTY_NAME = "dispatchPropertyName";
+  const TYPE_INFORMATION = 'typeInformation';
+  const GLOBAL_FUNCTIONS = 'globalFunctions';
+  const STATICS = 'statics';
+  const INTERCEPTED_NAMES = 'interceptedNames';
+  const MANGLED_GLOBAL_NAMES = 'mangledGlobalNames';
+  const MANGLED_NAMES = 'mangledNames';
+  const LIBRARIES = 'libraries';
+  const FINISHED_CLASSES = 'finishedClasses';
+  const ALL_CLASSES = 'allClasses';
+  const METADATA = 'metadata';
+  const INTERCEPTORS_BY_TAG = 'interceptorsByTag';
+  const LEAF_TAGS = 'leafTags';
+  const LAZIES = 'lazies';
+  const GET_ISOLATE_TAG = 'getIsolateTag';
+  const ISOLATE_TAG = 'isolateTag';
+  const CURRENT_SCRIPT = 'currentScript';
+  const DEFERRED_LIBRARY_URIS = 'deferredLibraryUris';
+  const DEFERRED_LIBRARY_HASHES = 'deferredLibraryHashes';
+  const INITIALIZE_LOADED_HUNK = 'initializeLoadedHunk';
+  const IS_HUNK_LOADED = 'isHunkLoaded';
+  const IS_HUNK_INITIALIZED = 'isHunkInitialized';
+  const DEFERRED_INITIALIZED = 'deferredInitialized';
+  const CLASS_ID_EXTRACTOR = 'classIdExtractor';
+  const CLASS_FIELDS_EXTRACTOR = 'classFieldsExtractor';
+  const INSTANCE_FROM_CLASS_ID = "instanceFromClassId";
+  const INITIALIZE_EMPTY_INSTANCE = "initializeEmptyInstance";
+  const TYPEDEF_TYPE_PROPERTY_NAME = "$typedefType";
+  const TYPEDEF_PREDICATE_PROPERTY_NAME = "$$isTypedef";
+  const NATIVE_SUPERCLASS_TAG_NAME = "$nativeSuperclassTag";
+  const MAP_TYPE_TO_INTERCEPTOR = "mapTypeToInterceptor";
   // Exports:
   exports.DISPATCH_PROPERTY_NAME = DISPATCH_PROPERTY_NAME;
   exports.TYPE_INFORMATION = TYPE_INFORMATION;
   exports.GLOBAL_FUNCTIONS = GLOBAL_FUNCTIONS;
   exports.STATICS = STATICS;
   exports.INTERCEPTED_NAMES = INTERCEPTED_NAMES;
   exports.MANGLED_GLOBAL_NAMES = MANGLED_GLOBAL_NAMES;
   exports.MANGLED_NAMES = MANGLED_NAMES;
   exports.LIBRARIES = LIBRARIES;
   exports.FINISHED_CLASSES = FINISHED_CLASSES;
@@ skipping 13 matching lines @@
   exports.DEFERRED_INITIALIZED = DEFERRED_INITIALIZED;
   exports.CLASS_ID_EXTRACTOR = CLASS_ID_EXTRACTOR;
   exports.CLASS_FIELDS_EXTRACTOR = CLASS_FIELDS_EXTRACTOR;
   exports.INSTANCE_FROM_CLASS_ID = INSTANCE_FROM_CLASS_ID;
   exports.INITIALIZE_EMPTY_INSTANCE = INITIALIZE_EMPTY_INSTANCE;
   exports.TYPEDEF_TYPE_PROPERTY_NAME = TYPEDEF_TYPE_PROPERTY_NAME;
   exports.TYPEDEF_PREDICATE_PROPERTY_NAME = TYPEDEF_PREDICATE_PROPERTY_NAME;
   exports.NATIVE_SUPERCLASS_TAG_NAME = NATIVE_SUPERCLASS_TAG_NAME;
   exports.MAP_TYPE_TO_INTERCEPTOR = MAP_TYPE_TO_INTERCEPTOR;
 });