Make modal based UI changes in TaskView only if modalness changes.

Fixes issue with jittery displaying of suggestion chip, when entering overview.
Merging into master manually as automerger failed.
Tested:Manual

Change-Id: I8228c51b22d550cb8f0aa559f997060b571763f1
(cherry picked from commit ed5e43bd25)

quickstep/src/com/android/quickstep/views/TaskView.java

@@ -323,6 +323,9 @@ public class TaskView extends FrameLayout implements PageCallbacks, Reusable {
      * @param modalness [0, 1] 0 being in context with other tasks, 1 being shown on its own.
      */
     public void setModalness(float modalness) {
+        if (mModalness == modalness) {
+            return;
+        }
         mModalness = modalness;
         mIconView.setAlpha(comp(modalness));
         if (mContextualChip != null) {