Move StringBufferImpl from coreimpl to core as _StringBufferImpl.

lib/coreimpl/string_buffer.dart

Index: lib/coreimpl/string_buffer.dart
diff --git a/lib/coreimpl/string_buffer.dart b/lib/coreimpl/string_buffer.dart
deleted file mode 100644
index ceb59350d3a43136d3f5eb0ccb9b0f84a25e7b22..0000000000000000000000000000000000000000
--- a/lib/coreimpl/string_buffer.dart
+++ /dev/null
@@ -1,86 +0,0 @@
-// Copyright (c) 2011, 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.
-
-/**
- * The StringBuffer class is useful for concatenating strings
- * efficiently. Only on a call to [toString] are the strings
- * concatenated to a single String.
- */
-class StringBufferImpl implements StringBuffer {
-  /**
-   * Creates the string buffer with an initial content.
-   */
-  StringBufferImpl(Object content) {
-    clear();
-    add(content);
-  }
-
-  /**
-   * Returns the length of the buffer.
-   */
-  int get length {
-    return _length;
-  }
-
-  bool isEmpty() {
-    return _length === 0;
-  }
-
-  /**
-   * Adds [obj] to the buffer. Returns [this].
-   */
-  StringBuffer add(Object obj) {
-    String str = obj.toString();
-    if (str === null || str.isEmpty()) {
-      return this;
-    }
-    _buffer.add(str);
-    _length += str.length;
-    return this;
-  }
-
-  /**
-   * Adds all items in [objects] to the buffer. Returns [this].
-   */
-  StringBuffer addAll(Collection objects) {
-    for (Object obj in objects) {
-      add(obj);
-    }
-    return this;
-  }
-
-  /**
-   * Adds the string representation of [charCode] to the buffer.
-   * Returns [this].
-   */
-  StringBuffer addCharCode(int charCode) {
-    return add(new String.fromCharCodes([charCode]));
-  }
-
-  /**
-   * Clears the string buffer. Returns [this].
-   */
-  StringBuffer clear() {
-    _buffer = new List<String>();
-    _length = 0;
-    return this;
-  }
-
-  /**
-   * Returns the contents of buffer as a concatenated string.
-   */
-  String toString() {
-    if (_buffer.length === 0) return "";
-    if (_buffer.length === 1) return _buffer[0];
-    String result = StringImplementation.concatAll(_buffer);
-    _buffer.clear();
-    _buffer.add(result);
-    // Since we track the length at each add operation, there is no
-    // need to update it in this function.
-    return result;
-  }
-
-  List<String> _buffer;
-  int _length;
-}