Fixes back button on action bar on some fragments.

SettingsPreferenceFragment has this already set so that the drawer
layout will work when the menu doesn't exist. However, some fragments
are not preference fragments, and we need to set setHasOptionsMenu
manually.

bug:27879503
Change-Id: I6faadeb56dab00af611ac413109800822038c66d

src/com/android/settings/OptionsMenuFragment.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016 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;
+
+import android.os.Bundle;
+
+/**
+ * Base class for a fragment that has the options menu.
+ * SettingsPreferenceFragment automatically sets this, but some activities do not use
+ * preferences, and we need to call setHasOptionsMenu(true) for the back button on action bar.
+ * For preference fragments, use SettingsPreferenceFragment.
+ */
+public abstract class OptionsMenuFragment extends InstrumentedFragment {
+
+    @Override
+    public void onActivityCreated(Bundle savedInstanceState) {
+        super.onActivityCreated(savedInstanceState);
+        setHasOptionsMenu(true);
+    }
+}