Fix long line.

lib/src/piece/piece.dart

@@ -108,8 +108,9 @@ abstract class Piece {
   void forEachChild(void Function(Piece piece) callback);
 
   /// If the piece can determine that it will always end up in a certain state
-  /// given [pageWidth] and size metrics returned by calling [containsHardNewline]
-  /// and [totalCharacters] on its children, then returns that [State].
+  /// given [pageWidth] and size metrics returned by calling
+  /// [containsHardNewline] and [totalCharacters] on its children, then returns
+  /// that [State].
   ///
   /// For example, a series of infix operators wider than a page will always
   /// split one per operator. If we can determine this eagerly just based on