Rewrite copyFile using Files.copy.

We had some tests observe incomplete copies pretty frequently, and this
seems to fix it. If for some reason this turns out to be noticeably less
efficient than FileChannel, we can rewrite it back to FileChannel and
loop to make sure it copies everything.

(Committed on behalf of a Googler.)

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

@@ -27,11 +27,13 @@
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
+import java.io.OutputStream;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.Reader;
 import java.nio.channels.FileChannel;
+import java.nio.file.Files;
 import java.util.List;
 
 /**
@@ -185,20 +187,12 @@ private static void copyFile(File from, File to, Filter onlyCopy) throws IOExcep
       return;
     }
 
-    FileChannel out = null;
-    FileChannel in = null;
-    try {
-      in = new FileInputStream(from).getChannel();
-      out = new FileOutputStream(to).getChannel();
-      final long length = in.size();
-
-      final long copied = in.transferTo(0, in.size(), out);
+    try (OutputStream out = new FileOutputStream(to)) {
+      final long copied = Files.copy(from.toPath(), out);
+      final long length = from.length();
       if (copied != length) {
         throw new IOException("Could not transfer all bytes.");
       }
-    } finally {
-      Closeables.close(out, false);
-      Closeables.close(in, false);
     }
   }