Properly clean up notification on download open

chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java

Index: chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java
index 91208d9774d8c44e8b3d39343b4be85c3543d6bf..fccde2811681e1e9e5361031942c67567e1cf5dd 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java
@@ -794,12 +794,14 @@ public class DownloadNotificationService extends Service {
     }
 
     /**
-     * Cancel a download notification.
+     * Removes a download notification and all associated tracking.  This method relies on the
+     * caller to provide the notification id, which is useful in the case where the internal
+     * tracking doesn't exist (e.g. in the case of a successful download, where we show the download
+     * completed notification and remove our internal state tracking).
      * @param notificationId Notification ID of the download
      * @param id The {@link ContentId} of the download.
      */
-    @VisibleForTesting
-    void cancelNotification(int notificationId, ContentId id) {
+    public void cancelNotification(int notificationId, ContentId id) {
         mNotificationManager.cancel(NOTIFICATION_NAMESPACE, notificationId);
         mDownloadSharedPreferenceHelper.removeSharedPreferenceEntry(id);
 
@@ -813,7 +815,8 @@ public class DownloadNotificationService extends Service {
     }
 
     /**
-     * Called when a download is canceled.
+     * Called when a download is canceled.  This method uses internal tracking to try to find the
+     * notification id to cancel.
      * @param id The {@link ContentId} of the download.
      */
     @VisibleForTesting