RFR: JDK-8227640: javac crashes on text blocks with invalid escapes.

[Jan Lahoda]

Hi,

When a text block contains an invalid escape sequence, there is an 
internal IllegalArgumentException thrown from String.translateEscapes 
invoked from javac. While this is concealed by javac, there are still 
ways to see the effects of the exception. So, I'd like to propose avoid 
calling String.translateEscapes when there are invalid escape sequences 
(errors for these invalid sequences are already reported).

JBS: https://bugs.openjdk.java.net/browse/JDK-8227640
Webrev: http://cr.openjdk.java.net/~jlahoda/8227640/webrev.00/

How does this look?

Thanks,
     Jan