Fix JS-backend when MirrorsUsed target a static field, but there is no mirrors usage.

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

 // Copyright (c) 2012, 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.
 
 part of js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 1732 matching lines @@
     // know if [mask] is not a more specific type than [indexing].
     return isTypedArray(mask) || mask.containsMask(indexing, compiler);
   }
 
   /// Called when [enqueuer] is empty, but before it is closed.
   void onQueueEmpty(Enqueuer enqueuer) {
     if (!enqueuer.isResolutionQueue && preMirrorsMethodCount == 0) {
       preMirrorsMethodCount = generatedCode.length;
     }
 
-    if (isTreeShakingDisabled) enqueuer.enqueueEverything();
+    if (isTreeShakingDisabled) {
+      enqueuer.enqueueEverything();
+    } else if (!targetsUsed.isEmpty) {
+      // Add all static elements (not classes) that have been requested for
+      // reflection. If there is no mirror-usage these are probably not
+      // necessary, but the backend relies on them being resolved.
+      List staticFields = [];

[kasperl, 2014/01/30 13:37:15]

If you only need them to be resolved, maybe you should not do this if the
enqueuer is the compilation queue? Maybe move the collects the static fields
somewhere else (just add a helper method).

[floitsch, 2014/01/30 14:10:24]

Done.

+      for (Element target in targetsUsed) {
+        if (target == null) continue;
+        if (target.isField()) {
+          staticFields.add(target);
+        } else if (target.isLibrary() || target.isClass()) {
+          ScopeContainerElement container = target;
+          container.forEachLocalMember((Element member) {
+            if (!member.isInstanceMember() && member.isField()) {
+              staticFields.add(member);
+            }
+          });
+        }
+      }
+      enqueuer.enqueueReflectiveStaticFields(staticFields);
+    }
 
     if (mustPreserveNames) compiler.log('Preserving names.');
 
     if (mustRetainMetadata) {
       compiler.log('Retaining metadata.');
 
       compiler.libraries.values.forEach(retainMetadataOf);
       for (Dependency dependency in metadataConstants) {
         registerCompileTimeConstant(
             dependency.constant, dependency.user);
@@ skipping 109 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }