Add optional writeAll separator argument.

sdk/lib/_internal/compiler/implementation/code_buffer.dart

 // Copyright (c) 2012, 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.
 
 part of dart2js;
 
 class CodeBuffer implements StringBuffer {
   StringBuffer buffer;
   List<CodeBufferMarker> markers;
   int lastBufferOffset = 0;
@@ skipping 19 matching lines @@
    */
   CodeBuffer write(var object) {
     if (object is CodeBuffer) {
       return addBuffer(object);
     }
     if (mappedRangeCounter == 0) setSourceLocation(null);
     buffer.write(object);
     return this;
   }
 
-  CodeBuffer writeAll(Iterable<Object> objects) {
+  CodeBuffer writeAll(Iterable<Object> objects, [String separator = ""]) {
+    bool isFirst = true;
     for (var object in objects) {
+      if (isFirst) {
+        isFirst = false;
+      } else {
+        if (separator != "") write(separator);
+      }
       write(object);
     }
     return this;
   }
 
   CodeBuffer writeln([var object = ""]) {
     return write(object).write("\n");
   }
 
   CodeBuffer addBuffer(CodeBuffer other) {
@@ skipping 58 matching lines @@
     });
   }
 }
 
 class CodeBufferMarker {
   final int offsetDelta;
   final sourcePosition;
 
   CodeBufferMarker(this.offsetDelta, this.sourcePosition);
 }