hg: jdk/sandbox: 8221307: String.substring() OOB exception on start index reports improper information

[chris.hegarty at oracle.com]

Changeset: a0257f1458aa
Author:    igerasim
Date:      2019-08-16 11:35 -0700
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/a0257f1458aa

8221307: String.substring() OOB exception on start index reports improper information
Reviewed-by: rriggs, redestad

! src/java.base/share/classes/java/lang/String.java
! src/java.base/share/classes/java/lang/StringUTF16.java
+ test/micro/org/openjdk/bench/java/lang/StringSubstring.java