Change analysis server protocol to omit empty lists when optional.

editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/TypeHierarchyItem.java

Index: editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/TypeHierarchyItem.java
diff --git a/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/TypeHierarchyItem.java b/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/TypeHierarchyItem.java
index 839767970287003ce1c6748f3e0c17fb45d49128..df915f8b65ae02d0dea2f2752a2a3891f267e7c2 100644
--- a/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/TypeHierarchyItem.java
+++ b/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/TypeHierarchyItem.java
@@ -119,9 +119,9 @@ public class TypeHierarchyItem {
     String displayName = jsonObject.get("displayName") == null ? null : jsonObject.get("displayName").getAsString();
     Element memberElement = jsonObject.get("memberElement") == null ? null : Element.fromJson(jsonObject.get("memberElement").getAsJsonObject());
     Integer superclass = jsonObject.get("superclass") == null ? null : jsonObject.get("superclass").getAsInt();
-    Integer[] interfaces = JsonUtilities.decodeIntegerArray(jsonObject.get("interfaces").getAsJsonArray());
-    Integer[] mixins = JsonUtilities.decodeIntegerArray(jsonObject.get("mixins").getAsJsonArray());
-    Integer[] subclasses = JsonUtilities.decodeIntegerArray(jsonObject.get("subclasses").getAsJsonArray());
+    Integer[] interfaces = jsonObject.get("interfaces") == null ? null : JsonUtilities.decodeIntegerArray(jsonObject.get("interfaces").getAsJsonArray());
+    Integer[] mixins = jsonObject.get("mixins") == null ? null : JsonUtilities.decodeIntegerArray(jsonObject.get("mixins").getAsJsonArray());
+    Integer[] subclasses = jsonObject.get("subclasses") == null ? null : JsonUtilities.decodeIntegerArray(jsonObject.get("subclasses").getAsJsonArray());
     return new TypeHierarchyItem(classElement, displayName, memberElement, superclass, interfaces, mixins, subclasses);
   }
 
@@ -206,21 +206,27 @@ public class TypeHierarchyItem {
     if (superclass != null) {
       jsonObject.addProperty("superclass", superclass);
     }
-    JsonArray jsonArrayInterfaces = new JsonArray();
-    for(Integer elt : interfaces) {
-      jsonArrayInterfaces.add(new JsonPrimitive(elt));
+    if (interfaces != null) {
+      JsonArray jsonArrayInterfaces = new JsonArray();
+      for(Integer elt : interfaces) {
+        jsonArrayInterfaces.add(new JsonPrimitive(elt));
+      }
+      jsonObject.add("interfaces", jsonArrayInterfaces);
     }
-    jsonObject.add("interfaces", jsonArrayInterfaces);
-    JsonArray jsonArrayMixins = new JsonArray();
-    for(Integer elt : mixins) {
-      jsonArrayMixins.add(new JsonPrimitive(elt));
+    if (mixins != null) {
+      JsonArray jsonArrayMixins = new JsonArray();
+      for(Integer elt : mixins) {
+        jsonArrayMixins.add(new JsonPrimitive(elt));
+      }
+      jsonObject.add("mixins", jsonArrayMixins);
     }
-    jsonObject.add("mixins", jsonArrayMixins);
-    JsonArray jsonArraySubclasses = new JsonArray();
-    for(Integer elt : subclasses) {
-      jsonArraySubclasses.add(new JsonPrimitive(elt));
+    if (subclasses != null) {
+      JsonArray jsonArraySubclasses = new JsonArray();
+      for(Integer elt : subclasses) {
+        jsonArraySubclasses.add(new JsonPrimitive(elt));
+      }
+      jsonObject.add("subclasses", jsonArraySubclasses);
     }
-    jsonObject.add("subclasses", jsonArraySubclasses);
     return jsonObject;
   }