Finish ChromeTabbedActivity if its tabs have been merged into another instance

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
index b1bafafddc97e1a2999df62c3d5430a6dbe55f7a..3193d1fc0170d7c5ee4fd560360a11eedd7d1436 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
@@ -186,6 +186,9 @@ public class ChromeTabbedActivity extends ChromeActivity implements OverviewMode
     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;
@@ -1093,6 +1096,14 @@ public class ChromeTabbedActivity extends ChromeActivity implements OverviewMode
     }
 
     @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();
     }
@@ -1197,6 +1208,8 @@ public class ChromeTabbedActivity extends ChromeActivity implements OverviewMode
                 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);
 
@@ -1616,6 +1629,8 @@ public class ChromeTabbedActivity extends ChromeActivity implements OverviewMode
         // 4. Ask TabPersistentStore to merge state.
         RecordUserAction.record("Android.MergeState.Live");
         mTabModelSelectorImpl.mergeState();
+
+        setMergedInstanceTaskId(getTaskId());
     }
 
     /**
@@ -1662,4 +1677,8 @@ public class ChromeTabbedActivity extends ChromeActivity implements OverviewMode
                 (ToolbarControlContainer) findViewById(R.id.control_container),
                 getTabModelSelector(), getControlContainerHeightResource(), true);
     }
+
+    private static void setMergedInstanceTaskId(int mergedInstanceTaskId) {
+        sMergedInstanceTaskId = mergedInstanceTaskId;
+    }
 }