[Android,MediaSession] Null check for sInstance if the service was restarted

chrome/android/java/src/org/chromium/chrome/browser/media/ui/NotificationMediaPlaybackControls.java

Index: chrome/android/java/src/org/chromium/chrome/browser/media/ui/NotificationMediaPlaybackControls.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/media/ui/NotificationMediaPlaybackControls.java b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/NotificationMediaPlaybackControls.java
index bc470d22402c649c87df031af240381f16327b86..935207ed9768f544bbf3f2dbcbaf1b6e6dc13b73 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/media/ui/NotificationMediaPlaybackControls.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/media/ui/NotificationMediaPlaybackControls.java
@@ -54,6 +54,12 @@ public class NotificationMediaPlaybackControls {
         @Override
         public void onCreate() {
             super.onCreate();
+
+            // This would only happen if we have been recreated by the OS after Chrome has died.
+            // In this case, there can be no media playback happening so we don't have to show
+            // the notification.
+            if (sInstance == null) return;
+
             onServiceStarted(this);
         }