Add new preference class MasterSwitchPreference.

- Add a new preference type that has Title and optional summary on the
  left, and a toggle switch on the right. Clicking the left part of the
  preference will open a settings screen.
- Update Connected devices->Bluetooth to use this new preference.
- Refactor BluetoothSettings and BluetoothEnabler to share code between
  the new bluetooth preference controller and the bluetooth setting.

Bug: 34280769
Test: make RunSettingsRoboTests
Change-Id: I109ecdba640ecdd4748a6e5b2b4f4c47cbf653fd

src/com/android/settings/widget/SwitchWidgetController.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2017 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.widget;
+
+/*
+ * A controller class for general switch widget handling. We have different containers that provide
+ * different forms of switch layout. Provide a centralized control for updating the switch widget.
+ */
+public abstract class SwitchWidgetController {
+
+    protected OnSwitchChangeListener mListener;
+
+    public interface OnSwitchChangeListener {
+        /**
+         * Called when the checked state of the Switch has changed.
+         *
+         * @param isChecked  The new checked state of switchView.
+         */
+        boolean onSwitchToggled(boolean isChecked);
+    }
+
+    public void setupView() {
+    }
+
+    public void teardownView() {
+    }
+
+    public void setListener(OnSwitchChangeListener listener) {
+        mListener = listener;
+    }
+
+    public abstract void updateTitle(boolean isChecked);
+
+    public abstract void startListening();
+
+    public abstract void stopListening();
+
+    public abstract void setChecked(boolean checked);
+
+    public abstract boolean isChecked();
+
+    public abstract void setEnabled(boolean enabled);
+
+}