Remove PrintWriter and PrintStringWriter from java_core.

pkg/analyzer/lib/src/dart/ast/ast.dart

Index: pkg/analyzer/lib/src/dart/ast/ast.dart
diff --git a/pkg/analyzer/lib/src/dart/ast/ast.dart b/pkg/analyzer/lib/src/dart/ast/ast.dart
index baeaddd9538e52303c26f10e8053f35a0e6a3fb4..73ab05ad8778bc8fbaf8e2775c5ae3df89cb458a 100644
--- a/pkg/analyzer/lib/src/dart/ast/ast.dart
+++ b/pkg/analyzer/lib/src/dart/ast/ast.dart
@@ -938,9 +938,9 @@ abstract class AstNodeImpl implements AstNode {
 
   @override
   String toSource() {
-    PrintStringWriter writer = new PrintStringWriter();
-    accept(new ToSourceVisitor(writer));
-    return writer.toString();
+    StringBuffer buffer = new StringBuffer();
+    accept(new ToSourceVisitor(buffer));
+    return buffer.toString();
   }
 
   @override