Strings: hardcode "\n" as the line separator

For android, it's already hardcoded in System.java

It was trying to use
System.getProperty("line.separator");
causing the class not to be compile-time initializable, causing
performance problems, see bug.

Bug: 28108158
Change-Id: I2a2549ce477d94e95e8239d97307eaaf50c05d6b
1 file changed