Generalize lookup-maps to support other const keys

pkg/compiler/lib/src/js_backend/backend.dart

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index f8ba2418a4879a8672c460d87c60ce836ed9e732..2ab5920b541b21c97991e70f1a6db03325974555 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -989,12 +989,8 @@ class JavaScriptBackend extends Backend {
     } else if (constant.isType) {
       enqueueInResolution(getCreateRuntimeType(), registry);
       registry.registerInstantiation(typeImplementation.rawType);
-      TypeConstantValue typeConstant = constant;
-      DartType representedType = typeConstant.representedType;
-      if (representedType != const DynamicType()) {
-        lookupMapAnalysis.registerTypeConstant(representedType.element);
-      }
     }
+    lookupMapAnalysis.registerConstantKey(constant);
   }
 
   void registerInstantiatedConstantType(DartType type, Registry registry) {