Use an enum in embedded_names as input to JS_GET_NAME.

pkg/compiler/lib/src/ssa/builder.dart

Index: pkg/compiler/lib/src/ssa/builder.dart
diff --git a/pkg/compiler/lib/src/ssa/builder.dart b/pkg/compiler/lib/src/ssa/builder.dart
index 40d87d147970ad8e7a8aaaf8fd493c7e93319a76..32965f3b6fe8447ac7b47975da97284a059f740a 100644
--- a/pkg/compiler/lib/src/ssa/builder.dart
+++ b/pkg/compiler/lib/src/ssa/builder.dart
@@ -3738,16 +3738,20 @@ class SsaBuilder extends ResolvedVisitor {
       }
       return;
     }
-    ast.LiteralString string = argument.asLiteralString();
-    if (string == null) {
+    Element element = elements[argument];
+    if (element == null ||
+        element is! FieldElement ||
+        element.enclosingClass != backend.jsGetNameEnum) {
       compiler.reportError(
           argument, MessageKind.GENERIC,
-          {'text': 'Error: Expected a literal string.'});
+          {'text': 'Error: Expected a JsGetName enum value.'});
     }
+    EnumClassElement enumClass = element.enclosingClass;
+    int index = enumClass.enumValues.indexOf(element);
     stack.add(
         addConstantString(
             backend.namer.getNameForJsGetName(
-                argument, string.dartString.slowToString())));
+                argument, JsGetName.values[index])));
   }
 
   void handleForeignJsEmbeddedGlobal(ast.Send node) {