Add instructions on how to annotate an AIDL interface

Fixes: 209500346
Test: m RUN_ERROR_PRONE=true framework |& grep -A 5 AndroidFrameworkRequiresPermission
Change-Id: If73e7c41543f3e8512e5ffe75e7620a6c4b0632b

errorprone/java/com/google/errorprone/bugpatterns/android/RequiresPermissionChecker.java

@@ -187,7 +187,10 @@ public final class RequiresPermissionChecker extends BugChecker
         if (!actualPerm.containsAll(expectedPerm)) {
             return buildDescription(tree)
                     .setMessage("Method " + method.name.toString() + "() annotated " + expectedPerm
-                            + " but too wide; only invokes methods requiring " + actualPerm)
+                            + " but too wide; only invokes methods requiring " + actualPerm
+                            + "\n  If calling an AIDL interface, it can be annotated by adding:"
+                            + "\n  @JavaPassthrough(annotation=\""
+                            + "@android.annotation.RequiresPermission(...)\")")
                     .build();
         }