fs.readFile: don't make the callback before the fd is closed

On Windows it is not possible to unlink() the read file in the callback.
This fixes #3051. A test is included.

lib/fs.js

@@ -78,18 +78,23 @@ fs.readFile = function(path, encoding_) {
   var readStream = fs.createReadStream(path);
   var buffers = [];
   var nread = 0;
+  var error;
 
   readStream.on('data', function(chunk) {
     buffers.push(chunk);
     nread += chunk.length;
   });
 
   readStream.on('error', function(er) {
-    callback(er);
+    error = er;
     readStream.destroy();
   });
 
-  readStream.on('end', function() {
+  readStream.on('close', function() {
+    if (error) {
+      return callback(error);
+    }
+
     // copy all the buffers into one
     var buffer;
     switch (buffers.length) {

test/simple/test-fs-readfile-unlink.js

@@ -0,0 +1,48 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var assert = require('assert'),
+    common = require('../common'),
+    fs = require('fs'),
+    path = require('path'),
+    dirName = path.resolve(common.fixturesDir, 'test-readfile-unlink'),
+    fileName = path.resolve(dirName, 'test.bin');
+
+var buf = new Buffer(512 * 1024);
+buf.fill(42);
+
+try {
+  fs.mkdirSync(dirName);
+} catch (e) {
+  // Ignore if the directory already exists.
+  if (e.code != 'EEXIST') throw e;
+}
+
+fs.writeFileSync(fileName, buf);
+
+fs.readFile(fileName, function(err, data) {
+  assert.ifError(err);
+  assert(data.length == buf.length);
+  assert.strictEqual(buf[0], 42);
+
+  fs.unlinkSync(fileName);
+  fs.rmdirSync(dirName);
+});