Add filename to IOException if file copy was failed.

* Add filename to IOException if file copy was failed.

I got the IOException "Could not transfer all bytes" and found that there was no glue what wrong.
filename may give a hint, at least.

* Change error message

change the error message - new version "Could not transfer all bytes from ... to ..."

Author: tirana

java/client/src/org/openqa/selenium/io/FileHandler.java

@@ -191,7 +191,7 @@ private static void copyFile(File from, File to, Filter onlyCopy) throws IOExcep
       final long copied = Files.copy(from.toPath(), out);
       final long length = from.length();
       if (copied != length) {
-        throw new IOException("Could not transfer all bytes.");
+        throw new IOException("Could not transfer all bytes from " + from + " to " + to);
       }
     }
   }