Do not dim the non-activated notifications on lockscreen

This fixes a lot of jank when showing all cards by tapping the more
card, because this lead to layer trashing in every frame (the
background was updated as well as the overall alpha for the card).

Bug: 17419967
Change-Id: Ib39af6eaab26409eedff72c921e9aa1ede31b830
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java b/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java
index 7c4c0e8..e4a1c27 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java
@@ -40,8 +40,6 @@
     private static final int MAX_ITEMS_IN_BOTTOM_STACK = 3;
     private static final int MAX_ITEMS_IN_TOP_STACK = 3;
 
-    /** When a child is activated, the other cards' alpha fade to this value. */
-    private static final float ACTIVATED_INVERSE_ALPHA = 0.9f;
     public static final float DIMMED_SCALE = 0.95f;
 
     private int mPaddingBetweenElements;
@@ -270,12 +268,8 @@
             childViewState.scale = !mScaleDimmed || !dimmed || isActivatedChild
                     ? 1.0f
                     : DIMMED_SCALE;
-            if (dimmed && activatedChild != null) {
-                if (!isActivatedChild) {
-                    childViewState.alpha *= ACTIVATED_INVERSE_ALPHA;
-                } else {
-                    childViewState.zTranslation += 2.0f * mZDistanceBetweenElements;
-                }
+            if (dimmed && isActivatedChild) {
+                childViewState.zTranslation += 2.0f * mZDistanceBetweenElements;
             }
         }
     }