Switch from the (unchecked) JSR305 annoation to the (checked) ErrorProne one
package com.google.javascript.jscomp.parsing.parser;
+import com.google.errorprone.annotations.Immutable;
import java.io.Serializable;
import java.util.Objects;
-import javax.annotation.concurrent.Immutable;
/**
* Represents various aspects of language version and support.
