Ensure formatted CUs end with a newline (dartbug.com/13188).

pkg/analyzer_experimental/lib/src/services/formatter_impl.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library formatter_impl;
 
 import 'dart:math';
 
 import 'package:analyzer_experimental/analyzer.dart';
 import 'package:analyzer_experimental/src/generated/parser.dart';
@@ skipping 437 matching lines @@
     var scriptTag = node.scriptTag;
     var directives = node.directives;
     visit(scriptTag);
 
     visitNodes(directives, separatedBy: newlines, followedBy: newlines);
 
     visitNodes(node.declarations, separatedBy: newlines);
 
     // Handle trailing whitespace
     token(node.endToken /* EOF */);
+    
+    // Be a good citizen, end with a NL
+    ensureTrailingNewline();
   }
 
   visitConditionalExpression(ConditionalExpression node) {
     visit(node.condition);
     space();
     token(node.question);
     space();
     visit(node.thenExpression);
     space();
     token(node.colon);
@@ skipping 735 matching lines @@
     append(' ');
   }
 
   /// Emit a breakable space
   breakableSpace() {
     //Implement
   }
 
   /// Append the given [string] to the source writer if it's non-null.
   append(String string) {
-    if (string != null) {
+    if (string != null && !string.isEmpty) {
       writer.print(string);
     }
   }
 
   /// Indent.
   indent() {
     writer.indent();
   }
 
   /// Unindent
@@ skipping 35 matching lines @@
       }
 
       previousToken = comment;
       comment = comment.next;
     }
 
     previousToken = token;
     return lines;
   }
 
+
+  ensureTrailingNewline() {
+    if (writer.lastToken is! NewlineToken) {
+      writer.newline();
+    }
+  }
+  
+  
   /// Test if this [comment] is at the end of a line.
   bool isAtEOL(Token comment) =>
       comment != null && comment.toString().trim().startsWith(twoSlashes) &&
       sameLine(comment, previousToken);
 
   /// Emit this [comment], inserting leading whitespace if appropriate.
   emitComment(Token comment, Token previousToken) {
     if (!writer.currentLine.isWhitespace() && !isBlock(comment)) {
       var ws = countSpacesBetween(previousToken, comment);
       // Preserve one space but no more
@@ skipping 69 matching lines @@
     var lastLine =
         lineInfo.getLocation(lastOffset).lineNumber;
     var currentLine =
         lineInfo.getLocation(currentOffset).lineNumber;
     return currentLine - lastLine;
   }
 
   String toString() => writer.toString();
 
 }