Added support for dumping AST to console, text file or dot file

compiler/java/com/google/dart/compiler/ast/viz/ASTWriterFactory.java

Index: compiler/java/com/google/dart/compiler/ast/viz/ASTWriterFactory.java
===================================================================
--- compiler/java/com/google/dart/compiler/ast/viz/ASTWriterFactory.java	(revision 0)
+++ compiler/java/com/google/dart/compiler/ast/viz/ASTWriterFactory.java	(revision 0)
@@ -0,0 +1,24 @@
+// 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.
+
+package com.google.dart.compiler.ast.viz;
+
+import com.google.dart.compiler.CompilerConfiguration;
+import com.google.dart.compiler.CommandLineOptions.CompilerOptions;
+
+public class ASTWriterFactory {
+  public static BaseASTWriter create(CompilerConfiguration config) {
+    String astFormat = config.getCompilerOptions().dumpAST();
+    CompilerOptions compilerOptions = config.getCompilerOptions();
+    String outDir = compilerOptions.getWorkDirectory().getAbsolutePath();
+    if ("console".equals(astFormat)) {
+      return new ConsoleWriter(outDir);
+    } else if ("text".equals(astFormat)) {
+      return new TextWriter(outDir);
+    } else if ("dot".equals(astFormat)) {
+      return new DotWriter(outDir);
+    }
+    return null;
+  }
+}