hg: amber/amber: Document preconditions for switch bootstraps; assert preconditions

[brian.goetz at oracle.com]

Changeset: f7e0fb7b2ce4
Author:    briangoetz
Date:      2018-03-07 10:34 -0500
URL:       http://hg.openjdk.java.net/amber/amber/rev/f7e0fb7b2ce4

Document preconditions for switch bootstraps; assert preconditions

! src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java