Add additional layout tests for MediaKeySession.keyStatuses

Source/modules/encryptedmedia/MediaKeyStatusMap.idl

Index: Source/modules/encryptedmedia/MediaKeyStatusMap.idl
diff --git a/Source/modules/encryptedmedia/MediaKeyStatusMap.idl b/Source/modules/encryptedmedia/MediaKeyStatusMap.idl
index dfd3a664f26e483ecd493edca78b378800c6bff6..27acc0ae89e497fc909b1e71051cd85c6dfcd909 100644
--- a/Source/modules/encryptedmedia/MediaKeyStatusMap.idl
+++ b/Source/modules/encryptedmedia/MediaKeyStatusMap.idl
@@ -22,8 +22,5 @@ typedef (ArrayBuffer or ArrayBufferView) BufferSource;
     [TreatReturnedNullStringAs=Undefined] MediaKeyStatus get(BufferSource key);
     boolean has(BufferSource key);
 
-    // FIXME: Implement forEach.
-    // void forEach (ForEachCallback callback);
-
     readonly maplike <BufferSource, MediaKeyStatus>;
 };