Enusre elderberry tabs remain after upgrade.

chrome/android/java/src/org/chromium/chrome/browser/document/ChromeLauncherActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/document/ChromeLauncherActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/document/ChromeLauncherActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/document/ChromeLauncherActivity.java
index b89385032af2dbc77e8ad093984ed8e083fa7ebc..bdd6ff1138b531ebbfcb6feeb2d531dc4a4ea0ac 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/document/ChromeLauncherActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/document/ChromeLauncherActivity.java
@@ -354,7 +354,8 @@ public class ChromeLauncherActivity extends Activity
 
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                 // Force a new document L+ to ensure the proper task/stack creation.
-                newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT);
+                newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT
+                        | Intent.FLAG_ACTIVITY_RETAIN_IN_RECENTS);
                 newIntent.setClassName(context, SeparateTaskCustomTabActivity.class.getName());
             } else {
                 int activityIndex =