8024788: (fs) Files.readAllBytes uses FileChannel which may not be supported by all providers

[Alan Bateman]

I need a reviewer for a small fix to Files.readAllBytes so that it works 
when the reading from a file associated with a FileSystemProvider that 
doesn't support FileChannel (which is allowed, 
FileSystemProvider.newFileChannel is allowed to throw UOE). This is one 
of the issues that Colin Decker brought up on this list a few weeks ago. 
The readAllBytes implementation can be trivially changed to see 
newByteChannel as per the discussion.

The webrev with the changes is here:

http://cr.openjdk.java.net/~alanb/8024788/webrev/

Thanks,
Alan.