Implement CHA through type mask and TypedSelector in the simple type inferrer.

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/js_backend/backend.dart	(revision 19615)
+++ sdk/lib/_internal/compiler/implementation/js_backend/backend.dart	(working copy)
@@ -642,6 +642,8 @@
   ClassElement jsFunctionClass;
   ClassElement jsNullClass;
   ClassElement jsBoolClass;
+  ClassElement typeLiteralClass;
+  ClassElement mapLiteralClass;
   Element jsArrayLength;
   Element jsStringLength;
   Element jsArrayRemoveLast;
@@ -840,6 +842,13 @@
     for (ClassElement cls in classes) {
       if (cls != null) interceptedClasses.add(cls);
     }
+
+    typeLiteralClass = compiler.findHelper(const SourceString('TypeImpl'));
+    // TODO(ngeoffray): We have ConstantMap and
+    // LinkedHashMapImplementation for literal maps. We should somehow
+    // have the users of [mapLiteralClass] know.
+    mapLiteralClass =
+        compiler.coreLibrary.find(const SourceString('LinkedHashMap'));
   }
 
   void addInterceptors(ClassElement cls, Enqueuer enqueuer) {
@@ -906,7 +915,7 @@
         // The backend will use a literal list to initialize the entries
         // of the map.
         enqueuer.registerInstantiatedClass(compiler.listClass);
-        enqueuer.registerInstantiatedClass(compiler.mapLiteralClass);
+        enqueuer.registerInstantiatedClass(mapLiteralClass);
         enqueueInResolution(getMapMaker());
       }
     }
@@ -1513,4 +1522,15 @@
   bool isNullImplementation(ClassElement cls) {
     return cls == jsNullClass;
   }
+
+  ClassElement get intImplementation => jsIntClass;
+  ClassElement get doubleImplementation => jsDoubleClass;
+  ClassElement get numImplementation => jsNumberClass;
+  ClassElement get stringImplementation => jsStringClass;
+  ClassElement get listImplementation => jsArrayClass;
+  ClassElement get mapImplementation => mapLiteralClass;
+  ClassElement get functionImplementation => jsFunctionClass;
+  ClassElement get typeImplementation => typeLiteralClass;
+  ClassElement get boolImplementation => jsBoolClass;
+  ClassElement get nullImplementation => jsNullClass;
 }