Merge changes Iebbc5d77,I2bef5f6f into udc-dev

* changes:
  Remove material U background for bouncer.
  Remove USE_NEW_ACTIVITY_STARTER flag

packages/SystemUI/res-keyguard/layout/keyguard_security_container_view.xml

@@ -19,9 +19,7 @@
 
 <com.android.keyguard.KeyguardSecurityContainer
     xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:androidprv="http://schemas.android.com/apk/prv/res/android"
     android:id="@+id/keyguard_security_container"
-    android:background="?androidprv:attr/materialColorSurfaceContainer"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:clipChildren="false"

packages/SystemUI/src/com/android/systemui/flags/Flags.kt

@@ -717,8 +717,4 @@ object Flags {
     @JvmField
     val SPLIT_SHADE_SUBPIXEL_OPTIMIZATION =
             unreleasedFlag(2805, "split_shade_subpixel_optimization", teamfood = true)
-
-    // TODO(b/278761837): Tracking Bug
-    @JvmField
-    val USE_NEW_ACTIVITY_STARTER = releasedFlag(2801, name = "use_new_activity_starter")
 }