Introduce SerializeDictionaryForest for devtools_target_ui

chrome/browser/devtools/serialize_dictionary_forest.h

Index: chrome/browser/devtools/serialize_dictionary_forest.h
diff --git a/chrome/browser/devtools/serialize_dictionary_forest.h b/chrome/browser/devtools/serialize_dictionary_forest.h
new file mode 100644
index 0000000000000000000000000000000000000000..428a2cacf474884fe7a04833d0cd45f3b6615564
--- /dev/null
+++ b/chrome/browser/devtools/serialize_dictionary_forest.h
@@ -0,0 +1,27 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_DEVTOOLS_SERIALIZE_DICTIONARY_FOREST_H_
+#define CHROME_BROWSER_DEVTOOLS_SERIALIZE_DICTIONARY_FOREST_H_
+
+#include <vector>
+
+#include "base/strings/string_piece.h"
+#include "base/values.h"
+
+// One node of a forest to be serialized by SerializeDictionaryForest.
+struct DictionaryForestNode {
+  DictionaryForestNode* parent;
+  base::DictionaryValue representation;
+};
+
+// A helper function taking a forest of Nodes and producing a ListValue
+// representation. The representation contains a list of DictionaryValue for
+// each root, and has DictionaryValues of children injected into a ListValue
+// keyed |child_key| in the parent's DictionaryValue.
+base::ListValue SerializeDictionaryForest(
+    std::vector<DictionaryForestNode> forest,
+    base::StringPiece child_key);
+
+#endif  // CHROME_BROWSER_DEVTOOLS_SERIALIZE_DICTIONARY_FOREST_H_