Enable Error Prone to detect obscure bugs.

We've been writing many new framework-specific Error Prone checkers
to help detect obscure platform bugs, and this change starts enabling
those checkers for more packages across the platform.

Bug: 155703208
Test: manual
Exempt-From-Owner-Approval: trivial blueprint changes
Change-Id: I1db3412b0be40f6f78c68331ae01756887192071
diff --git a/packages/SystemUI/Android.bp b/packages/SystemUI/Android.bp
index 80a6257..014d73f 100644
--- a/packages/SystemUI/Android.bp
+++ b/packages/SystemUI/Android.bp
@@ -163,6 +163,7 @@
 
 android_app {
     name: "SystemUI",
+    defaults: ["platform_app_defaults"],
     static_libs: [
         "SystemUI-core",
     ],
@@ -184,5 +185,4 @@
         "privapp_whitelist_com.android.systemui",
         "checked-wm_shell_protolog.json",
     ],
-
 }