bug#27692: 25.2; Indentation issue with strings in scheme mode

[Arun Isaac <arunisaac@systemreboot.net>]

I have the following text in an otherwise empty scheme mode buffer.

===file-begins-here===
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
(eiusmod tempor) incididunt ut labore et dolore (magna aliqua. Ut enim
ad)"
===file-ends-here===

I apply indent-region on the three lines, and they become:

===file-begins-here===
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
(eiusmod tempor) incididunt ut labore et dolore (magna aliqua. Ut enim
						       ad)"
===file-ends-here===

The parentheses in the string are wrongly indented as S-expressions.

However, if I have the following text in an otherwise empty scheme mode
buffer, indentation works correctly.

===file-begins-here===
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
incididunt ut labore et dolore (magna aliqua. Ut enim
ad)"
===file-ends-here===

Note that the only difference between the two text samples is the parentheses
around "eiusmod tempor". Also note that the buffer text is intended to be a
scheme string. So, the double quotes are part of the buffer text.

In GNU Emacs 25.2.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.22.15)
 of 2017-06-23