Add pathway to auto-migrate users when Chrome launches

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.document;
 
 import android.annotation.TargetApi;
 import android.content.Intent;
 import android.graphics.Bitmap;
 import android.graphics.Color;
@@ skipping 212 matching lines @@
 
     // Whether the page has started loading in this (browser) process once already. Must only be
     // used from the UI thread.
     private static boolean sIsFirstPageLoadStart = true;
 
     /** Whether the Tab has already been added to the TabModel. */
     private boolean mNeedsToBeAddedToTabModel;
 
     @Override
     protected boolean isStartedUpCorrectly(Intent intent) {
+        boolean isDocumentMode = FeatureUtilities.isDocumentMode(this);
         int tabId = ActivityDelegate.getTabIdFromIntent(getIntent());
-        boolean isDocumentMode = FeatureUtilities.isDocumentMode(this);
+
+        if (!isDocumentMode) {
+            // Fire a MAIN Intent to send the user back through ChromeLauncherActivity.
+            Log.e(TAG, "User is not in document mode.  Sending back to ChromeLauncherActivity.");
+
+            // Try to bring this tab forward after migration.
+            Intent tabbedIntent = null;
+            if (tabId != Tab.INVALID_TAB_ID) tabbedIntent = Tab.createBringTabToFrontIntent(tabId);
+
+            if (tabbedIntent == null) {
+                tabbedIntent = new Intent(Intent.ACTION_MAIN);
+                tabbedIntent.setPackage(getPackageName());
+            }
+
+            // Launch the other Activity in its own task so it stays when this one finishes.
+            tabbedIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+            tabbedIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT);
+
+            startActivity(tabbedIntent);
+            overridePendingTransition(0, 0);
+        }
+
         boolean isStartedUpCorrectly = tabId != Tab.INVALID_TAB_ID && isDocumentMode;
         if (!isStartedUpCorrectly) {
             Log.e(TAG, "Discarding Intent: Tab = " + tabId + ", Document mode = " + isDocumentMode);
         }
         return isStartedUpCorrectly;
     }
 
     @Override
     public void preInflationStartup() {
         // Decide whether to record startup UMA histograms. This is done  early in the main
@@ skipping 725 matching lines @@
 
     /**
      * Launch a new DocumentActivity showing the new tab page.
      * @param incognito Whether the new NTP should be in incognito mode.
      */
     private void launchNtp(boolean incognito) {
         if (incognito && !PrefServiceBridge.getInstance().isIncognitoModeEnabled()) return;
         getTabCreator(incognito).launchNTP();
     }
 }