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/Shell/Android.bp b/packages/Shell/Android.bp
index aaaf044..c873e30 100644
--- a/packages/Shell/Android.bp
+++ b/packages/Shell/Android.bp
@@ -1,5 +1,6 @@
 android_app {
     name: "Shell",
+    defaults: ["platform_app_defaults"],
     srcs: ["src/**/*.java",":dumpstate_aidl"],
     aidl: {
         include_dirs: ["frameworks/native/cmds/dumpstate/binder"],