[Android O] Initialize channels on first launch/upgrade

chrome/android/java/src/org/chromium/chrome/browser/notifications/ChannelsInitializer.java

Index: chrome/android/java/src/org/chromium/chrome/browser/notifications/ChannelsInitializer.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/notifications/ChannelsInitializer.java b/chrome/android/java/src/org/chromium/chrome/browser/notifications/ChannelsInitializer.java
index dfafe8deb3a348edc4639ccad8eaadea9475dec6..1f8ce6404c3e654cfde39863770414b63608a371 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/notifications/ChannelsInitializer.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/notifications/ChannelsInitializer.java
@@ -30,6 +30,11 @@ public class ChannelsInitializer {
     private @interface ChannelGroupId {}
     static final String CHANNEL_GROUP_ID_GENERAL = "general";
 
+    /**
+     * The set of predefined channels to be initialized on startup.
+     * {@link ChannelsUpdater#CHANNELS_VERSION} must be incremented every time an entry is modified,
+     * removed or added to this map.
+     */
     private static final Map<String, Channel> CHANNELS;
     static {
         Map<String, Channel> map = new HashMap<>();
@@ -59,6 +64,18 @@ public class ChannelsInitializer {
         mNotificationManager = notificationManagerProxy;
     }
 
+    public void initializeStartupChannels() {
+        for (@ChannelId String channelId : CHANNELS.keySet()) {
+            ensureInitialized(channelId);
+        }
+    }
+
+    void deleteAllChannels() {
+        for (String channelId : mNotificationManager.getNotificationChannelIds()) {
+            mNotificationManager.deleteNotificationChannel(channelId);
+        }
+    }
+
     /**
      * Ensures the given channel has been created on the notification manager so a notification
      * can be safely posted to it. This should only be used for channels that are predefined in
@@ -83,7 +100,7 @@ public class ChannelsInitializer {
      */
     public static class Channel {
         @ChannelId
-        final String mId;
+        public final String mId;
         final int mNameResId;
         final int mImportance;
         @ChannelGroupId