This is a follow-up fix for issues pointed out in the code review for JDK-8085822. Since that changeset went into verona/stage, the problems pointed out by the code review should be resolved in verona/stage before pushing to mainline.

Daniel D. Daugherty:
langtools/src/java.compiler/share/classes/javax/lang/model/SourceVersion.java
    old L171: case "1.9":
    new L171: case "9":
        Should this logic support both versions? Will dropping
        "1.9" here prevent a pre-version changeset JVM from
        being dropped into a JDK for triage purposes?

        Granted we don't often triage 'javac' with different JVMs, but...

Jan Lahoda:
+1 on keeping both "1.9" and "9" here. javac can be used independently on the rest of JDK to some extent, so support for running it on older builds of JDK 9 seems reasonable to me. (I wonder if current JDK 9 javac should be prepared for the new version scheme in advance.)