dart2js: add type lookup in the new emitter.

pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
index bc403c94db99a893210367e0efcef738feea8107..3f20f4fce1352b3b80fc399a2a7389169cf1422f 100644
--- a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
@@ -16,7 +16,8 @@ import 'package:_internal/compiler/js_lib/shared/embedded_names.dart' show
     DEFERRED_LIBRARY_HASHES,
     INITIALIZE_LOADED_HUNK,
     IS_HUNK_INITIALIZED,
-    IS_HUNK_LOADED;
+    IS_HUNK_LOADED,
+    GET_TYPE_FROM_NAME;
 
 import '../js_emitter.dart' show NativeGenerator;
 import '../model.dart';
@@ -135,7 +136,8 @@ class ModelEmitter {
                     new js.ObjectInitializer(const []))).toList())),
         js.js.statement('var holders = #', new js.ArrayInitializer(
             holders.map((e) => new js.VariableUse(e.name))
-                   .toList(growable: false)))
+                   .toList(growable: false))),
+        js.js.statement('var holdersMap = {}')
     ];
     return new js.Block(statements);
   }
@@ -155,6 +157,7 @@ class ModelEmitter {
       globals.add(emitInitializeLoadedHunk());
     }
 
+    globals.add(emitGetTypeFromName());
     js.ObjectInitializer globalsObject = new js.ObjectInitializer(globals);
 
     List<js.Statement> statements =
@@ -216,6 +219,15 @@ class ModelEmitter {
     return new js.Property(js.string(INITIALIZE_LOADED_HUNK), function);
   }
 
+  js.Property emitGetTypeFromName() {
+    js.Expression function =
+            js.js( """function(name) {
+                        var holder = holders[holdersMap[name]];
+                        return holder[name];
+                      }""");
+    return new js.Property(js.string(GET_TYPE_FROM_NAME), function);
+  }
+
   js.Expression emitDeferredFragment(DeferredFragment fragment,
                                      List<Holder> holders) {
     // TODO(floitsch): initialize eager classes.
@@ -415,6 +427,7 @@ class ModelEmitter {
     var classes = library[1];
     for (var i = 0; i < classes.length; i += 3) {
       var holderIndex = classes[i + 1];
+      holdersMap[classes[i]] = holderIndex;

[floitsch, 2015/01/23 10:46:31]

You can directly store the holder in the map.
That is: holdersMap[classes[i]] = holders[holderIndex]
Also makes the code above easier:

function(name) { return holdersMap[name][name]; }

[zarah, 2015/01/23 12:22:18]

Done.

       setupClass(classes[i], holders[holderIndex], classes[i + 2]);
     }
   }