Merge "No need to 'addChild' when start 'FLAG_ACTIVITY_CLEAR_TOP' Activity." am: 5fa55ef1c8 am: 5c917b8fdf

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1553956

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Iaa3e7e53814477d7c53dffdcad8daadac06de135