[Android Notifications] Enable FLAG_RECEIVER_FOREGROUND for N+

The flag ensures that the broadcast receiver for notification taps
gets foreground priority upon receiving the broadcast intent.

Bug: 868654
Change-Id: Ie45d039a3f0fb74fd40d467828ba2d7bf3e993ee
Reviewed-on: https://chromium-review.googlesource.com/968872Reviewed-by: Anita Woodruff <awdf@chromium.org>
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544334}

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

@@ -339,7 +339,7 @@ public class NotificationPlatformBridge {
         // This flag ensures the broadcast is delivered with foreground priority. It also means the
         // receiver gets a shorter timeout interval before it may be killed, but this is ok because
         // we schedule a job to handle the intent in NotificationService.Receiver on N+.
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
             intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);
         }