dart2js implementation of StringBuffer.writeAll that optimizes better

runtime/lib/string_buffer_patch.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.
 
 patch class StringBuffer {
   static const int _BUFFER_SIZE = 64;
   static const int _PARTS_TO_COMPACT = 128;
   static const int _PARTS_TO_COMPACT_SIZE_LIMIT = _PARTS_TO_COMPACT * 8;
 
   /**
@@ skipping 73 matching lines @@
         throw new RangeError.range(charCode, 0, 0x10FFFF);
       }
       _ensureCapacity(2);
       int bits = charCode - 0x10000;
       _buffer[_bufferPosition++] = 0xD800 | (bits >> 10);
       _buffer[_bufferPosition++] = 0xDC00 | (bits & 0x3FF);
       _bufferCodeUnitMagnitude |= 0xFFFF;
     }
   }
 
+  /* patch */ void writeAll(Iterable objects, [String separator = ""]) {
+    Iterator iterator = objects.iterator;
+    if (!iterator.moveNext()) return;
+    if (separator.isEmpty) {
+      do {
+        write(iterator.current);
+      } while (iterator.moveNext());
+    } else {
+      write(iterator.current);
+      while (iterator.moveNext()) {
+        write(separator);
+        write(iterator.current);
+      }
+    }
+  }
+
+  /* patch */ void writeln([Object obj = ""]) {
+    write(obj);
+    write("\n");
+  }
+
   /** Makes the buffer empty. */
   /* patch */ void clear() {
     _parts = null;
     _partsCodeUnits = _bufferPosition = _bufferCodeUnitMagnitude = 0;
   }
 
   /** Returns the contents of buffer as a string. */
   /* patch */ String toString() {
     _consumeBuffer();
     return (_partsCodeUnits == 0) ?
@@ skipping 60 matching lines @@
     _partsCodeUnitsSinceCompaction = 0;
     _partsCompactionIndex = _parts.length;
   }
 
   /**
    * Create a [String] from the UFT-16 code units in buffer.
    */
   static String _create(Uint16List buffer, int length, bool isLatin1)
       native "StringBuffer_createStringFromUint16Array";
 }