remove generated_sdk from checked in code

test/generated_sdk/lib/core/string_buffer.dart

-// 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.
-
-part of dart.core;
-
-/**
- * A class for concatenating strings efficiently.
- *
- * Allows for the incremental building of a string using write*() methods.
- * The strings are concatenated to a single string only when [toString] is
- * called.
- */
-class StringBuffer implements StringSink {
-
-  /** Creates the string buffer with an initial content. */
-  StringBuffer([Object content = ""]) : _contents = '$content';
-
-  /**
-   * Returns the length of the content that has been accumulated so far.
-   * This is a constant-time operation.
-   */
-  int get length => _contents.length;
-
-  /** Returns whether the buffer is empty. This is a constant-time operation. */
-  bool get isEmpty => length == 0;
-
-  /**
-   * Returns whether the buffer is not empty. This is a constant-time
-   * operation.
-   */
-  bool get isNotEmpty => !isEmpty;
-
-  /// Adds the contents of [obj], converted to a string, to the buffer.
-  void write(Object obj) {
-    _writeString('$obj');
-  }
-
-  /// Adds the string representation of [charCode] to the buffer.
-  void writeCharCode(int charCode) {
-    _writeString(new String.fromCharCode(charCode));
-  }
-
-  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);
-      }
-    }
-  }
-
-  void writeln([Object obj = ""]) {
-    write(obj);
-    write("\n");
-  }
-
-  /**
-   * Clears the string buffer.
-   */
-  void clear() {
-    _contents = "";
-  }
-
-  /// Returns the contents of buffer as a concatenated string.
-  String toString() => Primitives.flattenString(_contents);
-
-  String _contents;
-
-  void _writeString(str) {
-    _contents = Primitives.stringConcatUnchecked(_contents, str);
-  }
-}