[Background Sync] Use GcmNetworkManager to start the browser for sync events.

chrome/android/java/src/org/chromium/chrome/browser/BackgroundSyncLauncher.java

Index: chrome/android/java/src/org/chromium/chrome/browser/BackgroundSyncLauncher.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/BackgroundSyncLauncher.java b/chrome/android/java/src/org/chromium/chrome/browser/BackgroundSyncLauncher.java
new file mode 100644
index 0000000000000000000000000000000000000000..2192e6ab35faa5f53c7e183060305ababaa59965
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/BackgroundSyncLauncher.java
@@ -0,0 +1,196 @@
+// Copyright 2015 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;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.os.AsyncTask;
+import android.preference.PreferenceManager;
+
+import com.google.android.gms.gcm.GcmNetworkManager;
+import com.google.android.gms.gcm.OneoffTask;
+import com.google.android.gms.gcm.Task;
+
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.chrome.browser.externalauth.ExternalAuthUtils;
+import org.chromium.chrome.browser.externalauth.UserRecoverableErrorHandler;
+
+/**
+ * The {@link BackgroundSyncLauncher} singleton is created and owned by the C++ browser. It
+ * registers interest in waking up the browser the next time the device goes online after the
+ *browser closes via the {@link #setLaunchWhenNextOnline} method.

[jkarlin, 2015/10/20 17:45:56]

nit, add space between * and browser

[iclelland, 2015/10/20 18:56:06]

Done.

+ *
+ * Thread model: This class is to be run on the UI thread only.
+ */
+public class BackgroundSyncLauncher {
+    static final String PREF_BACKGROUND_SYNC_LAUNCH_NEXT_ONLINE = "bgsync_launch_next_online";
+    // The instance of BackgroundSyncLauncher currently owned by a C++
+    // BackgroundSyncLauncherAndroid, if any. If it is non-null then the browser is running.
+    private static BackgroundSyncLauncher sInstance;
+
+    private GcmNetworkManager mScheduler;
+
+    // Disables the automatic use of the GCMNetworkManager. When disabled, the methods which
+    // interact with GCM can still be used, but will not be called automatically on creation, or by
+    // {@link #launchBrowserWhenNextOnlineIfStopped}.
+    //
+    // Automatic GCM use is disabled by tests, and also by this class if it is determined on
+    // creation that the installed Play Services library is out of date.
+    private static boolean sGCMEnabled = true;

[dgn, 2015/10/19 20:01:31]

Nit: Why are those not javadoc comments (/** */)? Eclipse shows them on hover
when they are.

[iclelland, 2015/10/20 18:56:06]

No good reason. Thanks for pointing it out, will fix before committing.

+
+    /**
+     * Create a BackgroundSyncLauncher object, which is owned by C++.
+     * @param context The app context.
+     */
+    @VisibleForTesting
+    @CalledByNative
+    protected static BackgroundSyncLauncher create(Context context) {
+        if (sInstance != null) {
+            throw new IllegalStateException("Already instantiated");
+        }
+
+        sInstance = new BackgroundSyncLauncher(context);
+        return sInstance;
+    }
+
+    /**
+     * Called when the C++ counterpart is deleted.
+     */
+    @VisibleForTesting
+    @CalledByNative
+    protected void destroy() {
+        assert sInstance == this;
+        sInstance = null;
+    }
+
+    /**
+     * Callback for {@link #shouldLaunchWhenNextOnline}. The run method is invoked on the UI thread.
+     */
+    public static interface ShouldLaunchCallback { public void run(Boolean shouldLaunch); }
+
+    /**
+     * Returns whether the browser should be launched when the device next goes online.
+     * This is set by C++ and reset to false each time {@link BackgroundSyncLauncher}'s singleton is
+     * created (the native browser is started). This call is asynchronous and will run the callback
+     * on the UI thread when complete.
+     * @param context The application context.
+     * @param sharedPreferences The shared preferences.
+     */
+    protected static void shouldLaunchWhenNextOnline(
+            final Context context, final ShouldLaunchCallback callback) {
+        new AsyncTask<Void, Void, Boolean>() {
+            @Override
+            protected Boolean doInBackground(Void... params) {
+                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+                return prefs.getBoolean(PREF_BACKGROUND_SYNC_LAUNCH_NEXT_ONLINE, false);
+            }
+            @Override
+            protected void onPostExecute(Boolean shouldLaunch) {
+                callback.run(shouldLaunch);
+            }
+        }.execute();
+    }
+
+    /**
+     * Manages the scheduled tasks which re-launch the browser when the device next goes online.
+     * This method is called by C++ as background sync registrations are added and removed. When the
+     * {@link BackgroundSyncLauncher} singleton is created (on browser start), this is called to
+     * remove any pre-existing scheduled tasks.
+     */
+    @VisibleForTesting
+    @CalledByNative
+    protected void launchBrowserWhenNextOnlineIfStopped(
+            final Context context, final boolean shouldLaunch) {
+        new AsyncTask<Void, Void, Void>() {
+            @Override
+            protected Void doInBackground(Void... params) {
+                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+                prefs.edit()
+                        .putBoolean(PREF_BACKGROUND_SYNC_LAUNCH_NEXT_ONLINE, shouldLaunch)
+                        .apply();
+                return null;
+            }
+        }.execute();
+        if (sGCMEnabled) {

[jkarlin, 2015/10/20 17:45:56]

I think this condition should be run after the preferences have been written to
to keep things synchronized. AsyncTask has onPostExecute for that.

[iclelland, 2015/10/20 18:56:06]

Done.

+            if (shouldLaunch) {
+                scheduleLaunchTask(context, mScheduler);
+            } else {
+                removeScheduledTasks(mScheduler);
+            }
+        }
+    }
+
+    /**
+     * True if the native browser has started and created an instance of {@link
+     * BackgroundSyncLauncher}.
+     */
+    protected static boolean hasInstance() {
+        return sInstance != null;
+    }
+
+    protected BackgroundSyncLauncher(Context context) {
+        // Check to see if Play Services is up to date, and disable GCM if not.
+        // This will not automatically set {@link sGCMEnabled} to true, in case it has been disabled
+        // in tests.
+        if (sGCMEnabled && !canUseGooglePlayServices(context)) {
+            setGCMEnabled(false);
+        }
+        mScheduler = GcmNetworkManager.getInstance(context);
+        launchBrowserWhenNextOnlineIfStopped(context, false);
+    }
+
+    private boolean canUseGooglePlayServices(Context context) {
+        return ExternalAuthUtils.getInstance().canUseGooglePlayServices(
+                context, new UserRecoverableErrorHandler.Silent());
+    }
+
+    private static void scheduleLaunchTask(Context context, GcmNetworkManager scheduler) {
+        // Google Play Services may not be up to date, if the application was not installed through
+        // the Play Store. In this case, scheduling the task will fail silently.
+        OneoffTask oneoff = new OneoffTask.Builder()
+                                    .setService(BackgroundSyncLauncherService.class)
+                                    .setTag("BackgroundSync Event")
+                                    // We have to set a non-zero execution window here
+                                    .setExecutionWindow(0, 1)
+                                    .setRequiredNetwork(Task.NETWORK_STATE_CONNECTED)
+                                    .setPersisted(true)
+                                    .setUpdateCurrent(true)
+                                    .build();
+        scheduler.schedule(oneoff);
+    }
+
+    private static void removeScheduledTasks(GcmNetworkManager scheduler) {
+        scheduler.cancelAllTasks(BackgroundSyncLauncherService.class);
+    }
+
+    /**
+     * Reschedule any required background sync tasks, if they have been removed due to an
+     * application upgrade.
+     *
+     * This method checks the saved preferences, and reschedules the sync tasks as appropriate
+     * to match the preferences.
+     * This method is static so that it can be run without actually instantiating a
+     * BackgroundSyncLauncher.
+     */
+    protected static void rescheduleTasksOnUpgrade(final Context context) {
+        final GcmNetworkManager scheduler = GcmNetworkManager.getInstance(context);
+        BackgroundSyncLauncher.ShouldLaunchCallback callback =
+                new BackgroundSyncLauncher.ShouldLaunchCallback() {
+                    @Override
+                    public void run(Boolean shouldLaunch) {
+                        if (shouldLaunch) {
+                            scheduleLaunchTask(context, scheduler);
+                        }
+                    }
+                };
+        BackgroundSyncLauncher.shouldLaunchWhenNextOnline(context, callback);
+    }
+
+    @VisibleForTesting
+    static void setGCMEnabled(boolean enabled) {
+        sGCMEnabled = enabled;
+    }
+}