hg: jdk9/sandbox/jdk: 8143394: PushbackReader throws NullPointerException

[chris.hegarty at oracle.com]

Changeset: 0034a6f1ead1
Author:    bpb
Date:      2015-12-15 09:02 -0800
URL:       http://hg.openjdk.java.net/jdk9/sandbox/jdk/rev/0034a6f1ead1

8143394: PushbackReader throws NullPointerException
Summary: Synchronize on lock in close() to avoid NPE from read()-close() race.
Reviewed-by: alanb, dfuchs

! src/java.base/share/classes/java/io/CharArrayReader.java
! src/java.base/share/classes/java/io/PushbackReader.java
! src/java.base/share/classes/java/io/StringReader.java
+ test/java/io/PushbackReader/ReadCloseRaceNPE.java