DO NOT MERGE. Fix leak in LayoutTransition

LayoutTransition was making an incorrect assumption that there could
only be one transition animation on a child of a transitioning container.
But if multiple children are added/removed to/from that container, there would
be multiple calls to set up changing animations for each existing child
of that container. This meant that the child would have multiple, new
OnLayoutChangeListeners added to it as part of the setup process.

Meanwhile, we would cache only the latest listener in a hashmap that used
the child as a key for the listener. Then when we cleaned up the hashmap later,
we would remove only the latest listener from the child, leaving the rest there
for eternity.

The fix is to skip the setup entirely for children that already have listeners
set on them; they must, if that's the case, already have been set up and are
already listening for layout changes. Setting up the animation is redundant,
and adding another listener is a leak.

issue #5588509: memory leak in systemui

Change-Id: Ie2192593d84702be7243c18760dfdb3a027b761c

Author: chethaase

core/java/android/animation/LayoutTransition.java

@@ -657,6 +657,15 @@ public void setAnimateParentHierarchy(boolean animateParentHierarchy) {
      */
     private void setupChangeAnimation(final ViewGroup parent, final int changeReason,
             Animator baseAnimator, final long duration, final View child) {
+
+        // If we already have a listener for this child, then we've already set up the
+        // changing animation we need. Multiple calls for a child may occur when several
+        // add/remove operations are run at once on a container; each one will trigger
+        // changes for the existing children in the container.
+        if (layoutChangeListenerMap.get(child) != null) {
+            return;
+        }
+
         // Make a copy of the appropriate animation
         final Animator anim = baseAnimator.clone();