Add dynamic group panel

-Rename PanelCustomizedButtonCallback to PanelContentCallback
-Add onGroupChanged in PanelContentCallback
-Add test cases

Bug: 146813761
Test: make -j42 RunSettingsRoboTests
Change-Id: I60888efbbd0fc2878467418e55c70887a9d3f405

src/com/android/settings/panel/PanelContentCallback.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2020 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.android.settings.panel;
+
+/**
+ * PanelContentCallback provides a callback interface for {@link PanelFragment} to receive
+ * events from {@link PanelContent}.
+ */
+public interface PanelContentCallback {
+
+    /**
+     * It will be called when customized button state is changed. For example, custom button
+     * would be hidden for specific behavior.
+     */
+    void onCustomizedButtonStateChanged();
+
+    /**
+     * It will be called when group content is changed. For example, to add/remove a device into
+     * a group
+     */
+    void onGroupChanged();
+}