Add a GSI/DSU Loader to the developer option.

The Generic System Image (GSI) is a pure Android implementation with unmodified
Android Open Source Project (AOSP) code. The Dynamic System Updates (DSU) is a
Android Q feature that can download a system image and boot into it without the
factory rom being corrupted. This CL adds a DSU Loader which is a friendly
front-end that offers developers the ability to boot into GSI with one-click.
The DSU loader also offers the flexibility to overwrite the default setting
and load OEMs owned images.

Bug: 140090894
Test: click settings->developer option->debug::DSU Loader
    make -j32 RunSettingsRoboTests
Change-Id: Ia2a1b69b52047dd841dedf7f07b07f7ad3e65d46

src/com/android/settings/development/SelectDSUPreferenceController.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2019 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.development;
+
+import android.content.Context;
+import android.content.Intent;
+
+import androidx.preference.Preference;
+
+import com.android.settings.R;
+import com.android.settingslib.development.DeveloperOptionsPreferenceController;
+
+class SelectDSUPreferenceController extends DeveloperOptionsPreferenceController {
+
+    private static final String DSU_LOADER_KEY = "dsu_loader";
+
+    SelectDSUPreferenceController(Context context) {
+        super(context);
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return DSU_LOADER_KEY;
+    }
+
+    @Override
+    public boolean handlePreferenceTreeClick(Preference preference) {
+        if (DSU_LOADER_KEY.equals(preference.getKey())) {
+            final Intent intent = new Intent(mContext, DSULoader.class);
+            mContext.startActivity(intent);
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        preference.setSummary(mContext.getResources().getString(R.string.dsu_loader_description));
+    }
+}