Move stream-event JSON objects to a common package

This way they aren't so tied up with the ChangeHookRunner itself,
and we can start to reuse them for a gerrit query implementation.

Change-Id: If531bc193e3569f7df626c303cc8dc54be237ee0
Signed-off-by: Shawn O. Pearce <sop@google.com>

gerrit-server/src/main/java/com/google/gerrit/server/events/CommentAddedEvent.java

@@ -0,0 +1,24 @@
+// Copyright (C) 2010 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.events;
+
+public class CommentAddedEvent extends ChangeEvent {
+    public final String type = "comment-added";
+    public ChangeAttribute change;
+    public PatchSetAttribute patchSet;
+    public AccountAttribute author;
+    public ApprovalAttribute[] approvals;
+    public String comment;
+}