Don't share same name for js proxies cache.

sdk/lib/_internal/compiler/implementation/js_emitter/code_emitter_task.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.
 
 part of dart2js.js_emitter;
 
 /**
  * Generates the code for all used classes in the program. Static fields (even
  * in classes) are ignored, since they can be treated as non-class elements.
  *
@@ skipping 957 matching lines @@
                            Element isolateMain) {
     String mainAccess = "${namer.isolateStaticClosureAccess(appMain)}";
     // Since we pass the closurized version of the main method to
     // the isolate method, we must make sure that it exists.
     return "${namer.isolateAccess(isolateMain)}($mainAccess)";
   }
 
   jsAst.Expression generateDispatchPropertyInitialization() {
     return js('!#', js.fun([], [
 
-        // On V8, the 'intern' function converts a string to a symbol, which
-        // makes property access much faster.
-        new jsAst.FunctionDeclaration(new jsAst.VariableDeclaration('intern'),
-            js.fun(['s'], [
-                js('var o = {}'),
-                js('o[s] = 1'),
-                js.return_(js('Object.keys(convertToFastObject(o))[0]'))])),
-
         // To ensure that different programs loaded into the same context (page)
         // use distinct dispatch properies, we place an object on `Object` to
         // contain the names already in use.
         js('var tableProperty = "___dart_dispatch_property_names_"'),
         js('var usedProperties = Object[tableProperty] ||'
             '(Object[tableProperty] = Object.create(null))'),
 
         js('var rootProperty = "${generateDispatchPropertyName()}"'),
         js.for_('var i = 0', null, 'i++', [
-            js('property = intern(rootProperty + "_" + i + "_")'),
+            js('property = convertToJSSymbol(rootProperty + "_" + i + "_")'),
             js.if_('!(property in usedProperties)', [
                 js('usedProperties[property] = 1'),
                 js.return_(
                     js('init.dispatchPropertyName = property'))])])])());
   }
 
   String generateDispatchPropertyName() {
     // TODO(sra): MD5 of contributing source code or URIs?
     return '___dart_dispatch_record_ZxYxX_';
   }
@@ skipping 151 matching lines @@
     );
     jsAst.FunctionDeclaration decl = new jsAst.FunctionDeclaration(
         new jsAst.VariableDeclaration('init'), fun);
     buffer.write(jsAst.prettyPrint(decl, compiler).getText());
     if (compiler.enableMinification) buffer.write('\n');
   }
 
   void emitConvertToFastObjectFunction() {
     // Create an instance that uses 'properties' as prototype. This should make
     // 'properties' a fast object.
-    mainBuffer.add(r'''function convertToFastObject(properties) {
+    mainBuffer.add(r'''
+function convertToFastObject(properties) {
   function MyClass() {};
   MyClass.prototype = properties;
   new MyClass();
 ''');
     if (DEBUG_FAST_OBJECTS) {
       ClassElement primitives =
           compiler.findHelper('Primitives');
       FunctionElement printHelper =
           compiler.lookupElementIn(
               primitives, 'printString');
       String printHelperName = namer.isolateAccess(printHelper);
       mainBuffer.add('''
 // The following only works on V8 when run with option "--allow-natives-syntax".
 if (typeof $printHelperName === "function") {
   $printHelperName("Size of global object: "
                    + String(Object.getOwnPropertyNames(properties).length)
                    + ", fast properties " + %HasFastProperties(properties));
 }
 ''');
     }
-mainBuffer.add(r'''
+    mainBuffer.add(r'''
   return properties;
 }
 ''');
+    // On V8, the 'intern' function converts a string to a symbol, which
+    // makes property access much faster.
+    mainBuffer.add(r'''
+function convertToJSSymbol(s) {
+  var o = {};
+  o[s] = 1;
+  return Object.keys(convertToFastObject(o))[0];
+}
+''');
   }
 
   void writeLibraryDescriptors(LibraryElement library) {
     var uri = library.canonicalUri;
     if (uri.scheme == 'file' && compiler.sourceMapUri != null) {
       // TODO(ahe): It is a hack to use compiler.sourceMapUri
       // here.  It should be relative to the main JavaScript
       // output file.
       uri = relativize(
           compiler.sourceMapUri, library.canonicalUri, false);
@@ skipping 416 matching lines @@
     String sourceMap = buildSourceMap(mainBuffer, compiledFile);
     compiler.outputProvider(name, 'js.map')
         ..add(sourceMap)
         ..close();
   }
 
   void registerReadTypeVariable(TypeVariableElement element) {
     readTypeVariables.add(element);
   }
 }