Fix return to task when single task activity is brought to front

When a single task activity launched on top of home is relaunched
from another flow the return to task for the above activity is not
set correctly.

Adding a check and setting the returnto task to same as the
relaunched single task activity reurnto value ensures correct
activity is resumed.

CRs-Fixed: 830806
Change-Id: I3acf3e301ac3acd4e7aa69bdaf1cf7281b38c907

Author: Sashidhar Ganiga

services/core/java/com/android/server/am/ActivityStack.java

@@ -1957,6 +1957,12 @@ private void insertTaskAtTop(TaskRecord task) {
             ActivityStack lastStack = mStackSupervisor.getLastStack();
             final boolean fromHome = lastStack.isHomeStack();
             if (!isHomeStack() && (fromHome || topTask() != task)) {
+                if( !fromHome && task.isOverHomeStack()) {
+                    int taskNdx = mTaskHistory.indexOf(task);
+                    if ((taskNdx + 1) < mTaskHistory.size()) {
+                        mTaskHistory.get(taskNdx +1).setTaskToReturnTo(task.getTaskToReturnTo());
+                    }
+                }
                 task.setTaskToReturnTo(fromHome
                         ? lastStack.topTask() == null
                                 ? HOME_ACTIVITY_TYPE