Allow declared providers in attribute and aspect defintions.

--
PiperOrigin-RevId: 149169656
MOS_MIGRATED_REVID=149169656
diff --git a/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java b/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java
index 8cc374f..8e2ae52 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/AspectDefinition.java
@@ -300,9 +300,7 @@
      */
     public Builder advertiseProvider(ImmutableList<SkylarkProviderIdentifier> providers) {
       for (SkylarkProviderIdentifier provider : providers) {
-        // todo(dslomov,vladmos): support declared providers
-        Preconditions.checkState(provider.isLegacy());
-        advertisedProviders.addSkylark(provider.getLegacyId());
+        advertisedProviders.addSkylark(provider);
       }
       return this;
     }