Download notification: Never call stopForeground without startForeground.

This CL adds a boolean check for stopForeground that if startForeground
is not called, then ignore stopForeground call.

Bug: 1121096
Change-Id: I71295038925947472b0df7be2630a7cffbb79f97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2386421Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803529}

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

@@ -36,6 +36,10 @@ public class DownloadForegroundService extends Service {
 
     private NotificationManager mNotificationManager;
 
+    // Whether Service.startForeground is called. Notices Android will crash if
+    // Service.startForeground is not called when calling Service.stopForeground.
+    private boolean mStartForeground;
+
     @IntDef({StopForegroundNotification.KILL, StopForegroundNotification.DETACH})
     @Retention(RetentionPolicy.SOURCE)
     public @interface StopForegroundNotification {
@@ -231,6 +235,7 @@ public class DownloadForegroundService extends Service {
     @VisibleForTesting
     void startForegroundInternal(int notificationId, Notification notification) {
         Log.w(TAG, "startForegroundInternal id: " + notificationId);
+        mStartForeground = true;
         ForegroundServiceUtils.getInstance().startForeground(
                 this, notificationId, notification, 0 /* foregroundServiceType */);
     }
@@ -238,6 +243,10 @@ public class DownloadForegroundService extends Service {
     @VisibleForTesting
     void stopForegroundInternal(int flags) {
         Log.w(TAG, "stopForegroundInternal flags: " + flags);
+        if (!mStartForeground) {
+            Log.e(TAG, "stopForeground is called without startForeground.");
+            return;
+        }
         ForegroundServiceUtils.getInstance().stopForeground(this, flags);
     }