Finish ChromeTabbedActivity if its tabs have been merged into another instance

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.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;
 
 import android.annotation.TargetApi;
 import android.app.Activity;
 import android.app.ActivityManager;
 import android.content.Context;
@@ skipping 168 matching lines @@
     public static final String SKIP_FIRST_RUN_EXPERIENCE = "skip_first_run_experience";
 
     /**
      * Sending an intent with this action to Chrome will cause it to close all tabs
      * (iff the --enable-test-intents command line flag is set). If a URL is supplied in the
      * intent data, this will be loaded and unaffected by the close all action.
      */
     private static final String ACTION_CLOSE_TABS =
             "com.google.android.apps.chrome.ACTION_CLOSE_TABS";
 
+    /** The task id of the activity that tabs were merged into. */
+    private static int sMergedInstanceTaskId;
+
     private final ActivityStopMetrics mActivityStopMetrics = new ActivityStopMetrics();
 
     private FindToolbarManager mFindToolbarManager;
 
     private UndoBarController mUndoBarPopupController;
 
     private LayoutManagerChrome mLayoutManager;
 
     private ViewGroup mContentContainer;
 
@@ skipping 887 matching lines @@
                         (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
                 RecordHistogram.recordSparseSlowlyHistogram(
                         "MemoryAndroid.DeviceMemoryClass", am.getMemoryClass());
 
                 AutocompleteController.nativePrefetchZeroSuggestResults();
             }
         });
     }
 
     @Override
+    protected boolean isStartedUpCorrectly(Intent intent) {
+        // If tabs were merged into a different ChromeTabbedActivity instance, then this

[gone, 2016/10/25 18:33:10]

If tabs from this instance?

[Theresa, 2016/10/25 18:57:40]

Done.

+        // instance should not be created. This may happen if the process is restarted
+        // e.g. on upgrade or from about://flags. See crbug.com/657418
+        return sMergedInstanceTaskId == 0 || sMergedInstanceTaskId == getTaskId();

[gone, 2016/10/25 18:33:10]

I'm worried about cases where the user can't get back into Chrome because this
ID incorrectly stays set.  Should the merged instance task ID be reset in more
cases than the one below?  Does it make sense to reset it to 0 if
sMergedInstanceTaskId != getTaskId()?

[Theresa, 2016/10/25 18:57:40]

Done.

+    }
+
+    @Override
     public void terminateIncognitoSession() {
         getTabModelSelector().getModel(true).closeAllTabs();
     }
 
     @Override
     public boolean onMenuOrKeyboardAction(final int id, boolean fromMenu) {
         final Tab currentTab = getActivityTab();
         if (id == R.id.move_to_other_window_menu_id) {
             if (currentTab != null) moveTabToOtherWindow(currentTab);
         } else if (id == R.id.new_tab_menu_id) {
@@ skipping 84 matching lines @@
         } else {
             RecordUserAction.record("Android.LauncherShortcut.NewTab");
         }
     }
 
     private void moveTabToOtherWindow(Tab tab) {
         Class<? extends Activity> targetActivity =
                 MultiWindowUtils.getInstance().getOpenInOtherWindowActivity(this);
         if (targetActivity == null) return;
 
+        // When a second instance is created, the merged instance task id should be cleared.
+        setMergedInstanceTaskId(0);
         Intent intent = new Intent(this, targetActivity);
         MultiWindowUtils.setOpenInOtherWindowIntentExtras(intent, this, targetActivity);
 
         tab.detachAndStartReparenting(intent, null, null);
     }
 
     @Override
     public boolean handleBackPressed() {
         if (!mUIInitialized) return false;
         final Tab currentTab = getActivityTab();
@@ skipping 399 matching lines @@
                     break;
                 }
             }
             // 3. Kill the other activity's task to remove it from Android recents.
             otherActivityTask.finishAndRemoveTask();
         }
 
         // 4. Ask TabPersistentStore to merge state.
         RecordUserAction.record("Android.MergeState.Live");
         mTabModelSelectorImpl.mergeState();
+
+        setMergedInstanceTaskId(getTaskId());
     }
 
     /**
      * See VrShellDelegate#isVrShellEnabled()
      */
     @Override
     public boolean isVrShellEnabled() {
         return mVrShellDelegate.isVrShellEnabled();
     }
 
@@ skipping 26 matching lines @@
     public VrShellDelegate getVrShellDelegate() {
         return mVrShellDelegate;
     }
 
     @Override
     protected ChromeFullscreenManager createFullscreenManager() {
         return new ChromeFullscreenManager(this,
                 (ToolbarControlContainer) findViewById(R.id.control_container),
                 getTabModelSelector(), getControlContainerHeightResource(), true);
     }
+
+    private static void setMergedInstanceTaskId(int mergedInstanceTaskId) {
+        sMergedInstanceTaskId = mergedInstanceTaskId;
+    }
 }