Add PhysicalWebBroadcastService

chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PhysicalWebBroadcastService.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.physicalweb;
+
+import android.annotation.TargetApi;
+import android.app.Service;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.os.Build;
+import android.os.IBinder;
+
+import org.chromium.base.ContextUtils;
+
+/**
+ * Broadcasts Physical Web URLs via Bluetooth Low Energy (BLE).
+ *
+ * This background service will start when the user activates the Physical Web Sharing item in the
+ * sharing chooser intent. If the URL received from the triggering Tab is a validated

[nyquist, 2017/03/07 06:58:33]

Remove " a " 

[iankc, 2017/03/07 18:03:08]

Done.

+ * by the Physical Web Service then it will encode the URL into an Eddystone URL and
+ * broadcast the URL through BLE.
+ *
+ * To notify and provide the user with the ability to terminate broadcasting
+ * a persistent notification with a cancel button will be created. This cancel button will stop the
+ * service and will be the only way for the user to stop the serive.
+ *
+ * If the user terminates Chrome or the OS shutsdown this service mid-broadcasting, when the service

[nyquist, 2017/03/07 06:58:33]

"shuts down"

[iankc, 2017/03/07 18:03:08]

Done.

+ * get's restarted it will restart broadcasting as well by gathering the URL from shared
+ * preferences. This will create a seemless experience to the user by behaving as though
+ * broadcasting is not connected to the Chrome application.
+ *
+ * bluetooth.le.AdvertiseCallback and bluetooth.BluetoothAdapter require API level 21.
+ * This will only be run on M and above.
+ **/
+
+@TargetApi(Build.VERSION_CODES.LOLLIPOP)
+public class PhysicalWebBroadcastService extends Service {
+    public static final String DISPLAY_URL_KEY = "display_url";
+
+    public static final String PREVIOUS_BROADCAST_URL_KEY = "previousUrl";
+
+    private boolean mStartedByRestart;

[nyquist, 2017/03/07 06:58:33]

Is the plan to use this for something later? Otherwise, it could be a local
variable. The JavaDoc hints to that this will be used in the future maybe
though.

[iankc, 2017/03/07 18:03:08]

Yeah, there are minor changes to the procedure when it is "startedByRestart", so
it's useful to make it an instance attribute.

+
+    @Override
+    public int onStartCommand(Intent intent, int flags, int startId) {
+        String displayUrl = intent.getStringExtra(DISPLAY_URL_KEY);

[nyquist, 2017/03/07 06:58:33]

I think you want to call fetchBroadcastData() here.

[iankc, 2017/03/07 18:03:08]

Done.

+
+        // This should never happen.
+        if (displayUrl == null) {
+            stopSelf();
+            return START_STICKY;
+        }
+
+        // TODO(iankc): implement parsing, broadcasting, and notifications.
+        stopSelf();
+        return START_STICKY;
+    }
+
+    @Override
+    public IBinder onBind(Intent intent) {
+        return null;
+    }
+
+    private String fetchBroadcastData(Intent intent) {

[nyquist, 2017/03/07 06:58:33]

For now, this just retrieves the display URL, so maybe just use that as a method
name too, until it expands to return something more? I.e. fetchDisplayUrl(...)?

[iankc, 2017/03/07 18:03:08]

Done.

+        String displayUrl;
+
+        mStartedByRestart = intent == null;

[nyquist, 2017/03/07 06:58:33]

I like that you split this out to a variable to signify what a null-intent
means. Thanks!

[iankc, 2017/03/07 18:03:08]

Done.

+        if (mStartedByRestart) {
+            SharedPreferences sharedPrefs = ContextUtils.getAppSharedPreferences();
+            displayUrl = sharedPrefs.getString(PREVIOUS_BROADCAST_URL_KEY, null);

[nyquist, 2017/03/07 06:58:33]

You can probably just return this directly here, especially if you change the
method name.

[iankc, 2017/03/07 18:03:08]

Done.

+            return displayUrl;
+        }
+
+        displayUrl = intent.getStringExtra(DISPLAY_URL_KEY);

[nyquist, 2017/03/07 06:58:33]

I'd just declare displayUrl here.

[iankc, 2017/03/07 18:03:08]

Done.

+        ContextUtils.getAppSharedPreferences()
+                .edit()
+                .putString(PREVIOUS_BROADCAST_URL_KEY, displayUrl)
+                .commit();
+        return displayUrl;
+    }
+}