When metadata is not requested, elide unneeded signatures

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart

 // Copyright (c) 2015, 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.
 
 /// This library defines the operations that define and manipulate Dart
 /// classes.  Included in this are:
 ///   - Generics
 ///   - Class metadata
 ///   - Extension methods
 ///
@@ skipping 32 matching lines @@
     // Run base initializer.
     $base.prototype.new.apply(this, args);
   };
 
   // Set the signature of the Mixin class to be the composition
   // of the signatures of the mixins.
   $setSignature(Mixin, {
     methods: () => {
       let s = {};
       for (let m of $mixins) {
-        $copyProperties(s, m[$_methodSig]);
+        if (m[$_methodSig]) $copyProperties(s, m[$_methodSig]);
       }
       return s;
     },
     fields: () => {
       let s = {};
       for (let m of $mixins) {
-        $copyProperties(s, m[$_fieldSig]);
+        if (m[$_fieldSig]) $copyProperties(s, m[$_fieldSig]);
       }
       return s;
     },
     getters: () => {
       let s = {};
       for (let m of $mixins) {
-        $copyProperties(s, m[$_getterSig]);
+        if (m[$_getterSig]) $copyProperties(s, m[$_getterSig]);
       }
       return s;
     },
     setters: () => {
       let s = {};
       for (let m of $mixins) {
-        $copyProperties(s, m[$_setterSig]);
+        if (m[$_setterSig]) $copyProperties(s, m[$_setterSig]);
       }
       return s;
     }
   });
 
   // Save mixins for reflection
   Mixin[$_mixins] = $mixins;
   return Mixin;
 })()''');
 
@@ skipping 408 matching lines @@
   let jsProto = $jsType.prototype;
 
   // TODO(vsm): This sometimes doesn't exist on FF.  These types will be
   // broken.
   if (!jsProto) return;
 
   // Mark the JS type's instances so we can easily check for extensions.
   jsProto[$_extensionType] = $dartExtType;
   $_installProperties(jsProto, extProto);
   function updateSig(sigF) {
-    let originalSigFn = $getOwnPropertyDescriptor($dartExtType, sigF).get;
+    let originalDesc = $getOwnPropertyDescriptor($dartExtType, sigF);
+    if (originalDesc === void 0) return;
+    let originalSigFn = originalDesc.get;
     $assert_(originalSigFn);
     $defineMemoizedGetter($jsType, sigF, originalSigFn);
   }
   updateSig($_methodSig);
   updateSig($_fieldSig);
   updateSig($_getterSig);
   updateSig($_setterSig);
 })()''');
 
 ///
@@ skipping 24 matching lines @@
     $defineProperty(proto, $getExtensionSymbol(name), method);
   }
   // Ensure the signature is available too.
   // TODO(jmesserly): not sure if we can do this in a cleaner way. Essentially
   // we need to copy the signature (and in the future, other data like
   // annotations) any time we copy a method as part of our metaprogramming.
   // It might be more friendly to JS metaprogramming if we include this info
   // on the function.
 
   function upgradeSig(sigF) {
-    let originalSigFn = $getOwnPropertyDescriptor($type, sigF).get;
+    let originalSigDesc = $getOwnPropertyDescriptor($type, sigF);
+    if (originalSigDesc === void 0) return;
+    let originalSigFn = originalSigDesc.get;
     $defineMemoizedGetter(type, sigF, function() {
       let sig = originalSigFn();
       let propertyNames = Object.getOwnPropertyNames(sig);
       for (let name of methodNames) {
         if (name in sig) {
           sig[$getExtensionSymbol(name)] = sig[name];
         }
       }
       return sig;
     });
@@ skipping 75 matching lines @@
     '''(() => {
   let values = [];
   for (var i = 0; i < $names.length; i++) {
     let value = $const_(new $enumClass(i));
     values.push(value);
     Object.defineProperty($enumClass, $names[i],
         { value: value, configurable: true });
   }
   $enumClass.values = $constList(values, $enumClass);
 })()''');