Refactor chromedriver's script execution to reduce amount of custom Value parsing.

chrome/test/webdriver/webdriver_util.h

+// Copyright (c) 2011 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_TEST_WEBDRIVER_WEBDRIVER_UTIL_H_
+#define CHROME_TEST_WEBDRIVER_WEBDRIVER_UTIL_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "chrome/test/automation/value_conversion_traits.h"
+
+namespace base {
+class Value;
+}
+
+namespace webdriver {
+
+// Generates a random, 32-character hexidecimal ID.
+std::string GenerateRandomID();
+
+// Returns the equivalent JSON string for the given value.
+std::string JsonStringify(const base::Value* value);
+
+// Parses a given value.
+class ValueParser {
+ public:
+  virtual ~ValueParser();
+  virtual bool Parse(base::Value* value) const = 0;
+
+ protected:
+  ValueParser();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ValueParser);
+};
+
+// Define a special type and constant that allows users to skip parsing a value.
+// Useful when wanting to skip parsing for one value out of many in a list.
+enum SkipParsing { };
+extern SkipParsing* kSkipParsing;
+
+// Parses a given value using the |ValueConversionTraits| to the appropriate
+// type. This assumes that a direct conversion can be performed without
+// pulling the value out of a dictionary or list.
+template <typename T>
+class DirectValueParser : public ValueParser {
+ public:
+  explicit DirectValueParser(T* t) : t_(t) { }
+
+  virtual ~DirectValueParser() { }
+
+  virtual bool Parse(base::Value* value) const OVERRIDE {
+    return ValueConversionTraits<T>::SetFromValue(value, t_);
+  }
+
+ private:
+  T* t_;
+  DISALLOW_COPY_AND_ASSIGN(DirectValueParser);
+};
+
+// Convenience function for creating a DirectValueParser.
+template <typename T>
+DirectValueParser<T>* CreateDirectValueParser(T* t) {
+  return new DirectValueParser<T>(t);
+}
+
+}  // namespace webdriver
+
+// Value conversion traits for SkipParsing, which just return true.
+template <>
+struct ValueConversionTraits<webdriver::SkipParsing> {
+  static bool SetFromValue(const base::Value* value,
+                           const webdriver::SkipParsing* t);
+  static bool CanConvert(const base::Value* value);
+};
+
+#endif  // CHROME_TEST_WEBDRIVER_WEBDRIVER_UTIL_H_