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

chrome/test/webdriver/web_element_id.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_WEB_ELEMENT_ID_H_
 #define CHROME_TEST_WEBDRIVER_WEB_ELEMENT_ID_H_
 #pragma once
 
 #include <string>
 
+#include "chrome/test/automation/value_conversion_traits.h"
+
 namespace base {
 class Value;
 }
 
 namespace webdriver {
 
 // This class represents a WebDriver WebElement ID. These IDs are mapped to
 // objects in a page in JavaScript.
 class WebElementId {
  public:
   // Creates an invalid WebElementId.
   WebElementId();
 
   // Creates a valid |WebElementId| using the ID of an element. An empty string
   // can be used to refer to the root document of the page.
   explicit WebElementId(const std::string& id);
 
   // Creates a |WebElementId| from an element dictionary returned by a WebDriver
   // atom. It will be valid iff the dictionary is correctly constructed.
-  explicit WebElementId(base::Value* value);
+  explicit WebElementId(const base::Value* value);
 
   ~WebElementId();
 
   // Returns the appropriate |Value| type to be used to identify the element
   // to a WebDriver atom. The client takes ownership.
   base::Value* ToValue() const;
 
   // Returns whether this ID is valid. Even if the ID is valid, it may not refer
   // to a valid ID on the page.
   bool is_valid() const;
@@ skipping 12 matching lines @@
   static const char kId[];
   static const char kLinkText[];
   static const char kName[];
   static const char kPartialLinkText[];
   static const char kTagName[];
   static const char kXpath[];
 };
 
 }  // namespace webdriver
 
+template <>
+struct ValueConversionTraits<webdriver::WebElementId> {
+  static base::Value* CreateValueFrom(const webdriver::WebElementId& t);
+  static bool SetFromValue(
+      const base::Value* value, webdriver::WebElementId* t);
+  static bool CanConvert(const base::Value* value);
+};
+
 #endif  // CHROME_TEST_WEBDRIVER_WEB_ELEMENT_ID_H_