QS Header: don't update everything unless we need to

Because it leads to bad performance.

Bug: 30442298
Change-Id: I4c7b68ad30a1fd4fe8245f27ce2d2b2038583d23

packages/SystemUI/src/com/android/systemui/statusbar/phone/QuickStatusBarHeader.java

@@ -197,6 +197,7 @@ public class QuickStatusBarHeader extends BaseStatusBarHeader implements
 
     @Override
     public void setExpanded(boolean expanded) {
+        if (mExpanded == expanded) return;
         mExpanded = expanded;
         mHeaderQsPanel.setExpanded(expanded);
         updateEverything();