Revert "Add StringSink and update StringBuffer."

sdk/lib/core/string_buffer.dart

Index: sdk/lib/core/string_buffer.dart
diff --git a/sdk/lib/core/string_buffer.dart b/sdk/lib/core/string_buffer.dart
index 2de49498aa19b29b68fdef0356aed9e8fba78711..d8b393583952238a7e66027ba20d0b45b86179e4 100644
--- a/sdk/lib/core/string_buffer.dart
+++ b/sdk/lib/core/string_buffer.dart
@@ -9,77 +9,29 @@ part of dart.core;
  * efficiently. Only on a call to [toString] are the strings
  * concatenated to a single String.
  */
-class StringBuffer implements StringSink {
+abstract class StringBuffer {
 
   /// Creates the string buffer with an initial content.
-  external StringBuffer([Object content = ""]);
+  external factory StringBuffer([Object content = ""]);
 
   /// Returns the length of the buffer.
-  external int get length;
+  int get length;
 
-  /// Returns whether the buffer is empty.
-  bool get isEmpty => length == 0;
+  // Returns whether the buffer is empty.
+  bool get isEmpty;
 
-  /**
-   * Converts [obj] to a string and adds it to the buffer.
-   *
-   * *Deprecated*. Use [write] instead.
-   */
-  @deprecated
-  void add(Object obj) => write(obj);
-
-  void write(Object obj) {
-    // TODO(srdjan): The following four lines could be replaced by
-    // '$obj', but apparently this is too slow on the Dart VM.
-    String str = obj.toString();
-    if (str is! String) {
-      throw new ArgumentError('toString() did not return a string');
-    }
-    if (str.isEmpty) return;
-    _write(str);
-  }
-
-
-  void print(Object obj) {
-    write(obj);
-    _write("\n");
-  }
-
-  /**
-   * Adds the string representation of [charCode] to the buffer.
-   *
-   * *Deprecated* Use [writeCharCode] instead.
-   */
-  @deprecated
-  void addCharCode(int charCode) {
-    writeCharCode(charCode);
-  }
+  /// Converts [obj] to a string and adds it to the buffer.
+  void add(Object obj);
 
   /// Adds the string representation of [charCode] to the buffer.
-  void writeCharCode(int charCode) {
-    _write(new String.fromCharCode(charCode));
-  }
+  void addCharCode(int charCode);
 
-  /**
-   * Adds all items in [objects] to the buffer.
-   *
-   * *Deprecated*. Use [:objects.forEach(buffer.write):] instead.
-   */
-  @deprecated
-  void addAll(Iterable objects) {
-    for (Object obj in objects) write(obj);
-  }
+  /// Adds all items in [objects] to the buffer.
+  void addAll(Iterable objects);
 
-  /**
-   * Clears the string buffer.
-   *
-   * *Deprecated*.
-   */
-  @deprecated
-  external void clear();
+  /// Clears the string buffer.
+  void clear();
 
   /// Returns the contents of buffer as a concatenated string.
-  external String toString();
-
-  external void _write(String str);
+  String toString();
 }