Remove hotseat flicker and all apps GPU overdraw

> Short story: elevation + transparency caused both flicker and overdraw

b/29641308
b/29648104

Change-Id: I621ccd888fa4c7e9292336dac1371246115cd3bb
diff --git a/res/layout/all_apps.xml b/res/layout/all_apps.xml
index d55fda7..c4c6aab 100644
--- a/res/layout/all_apps.xml
+++ b/res/layout/all_apps.xml
@@ -31,7 +31,6 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:layout_gravity="center"
-        android:elevation="2dp"
         android:focusable="false"
         android:visibility="invisible" />
 
@@ -41,7 +40,6 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:layout_gravity="center"
-        android:elevation="15dp"
         android:focusable="true"
         android:focusableInTouchMode="true"
         android:saveEnabled="false"