8073640: Nashorn scripting: here document with only whitespace gives error

Added support for handling trailing blank lines in here-doc string parsing

Reviewed-by: hannesw, jlaskey

nashorn/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/parser/Lexer.java

@@ -1605,6 +1605,10 @@ public class Lexer extends Scanner {
                 // Skip any whitespace.
                 skipWhitespace(false);
 
+                //handle trailing blank lines
+                lastLinePosition = position;
+                stringEnd = position;
+
                 if (hasHereMarker(identStart, identLength)) {
                     break;
                 }

nashorn/test/script/basic/JDK-8073640.js

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * JDK-8073640: Nashorn scripting: here document with only whitespace gives error
+ *
+ * @test
+ * @option -scripting
+ * @run
+ */
+
+/*case 1*/
+print(<<EOD);
+
+EOD
+
+/*case 2*/
+print(<<EOD);
+
+line2
+line3
+EOD
+
+/*case 3*/
+print(<<EOD);
+line1
+
+line3
+EOD
+
+/*case 4*/
+print(<<EOD);
+line1
+line2
+
+EOD
+
+/*case 5*/
+print(<<EOD);
+
+line2
+
+line4
+
+EOD

nashorn/test/script/basic/JDK-8073640.js.EXPECTED

@@ -0,0 +1,15 @@
+
+
+line2
+line3
+line1
+
+line3
+line1
+line2
+
+
+line2
+
+line4
+