Be more tolerant in TaskStackBuilder
Be more tolerant in TaskStackBuilder

Let callers try to get a parent stack for an activity class with no
parent declared.

Bug 6503702

Change-Id: Iec1bc7a8d9e5b65b756a8ebd0e53d63506796aa3

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base