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

chrome/test/webdriver/web_element_id.cc

 // 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.
 
 #include "chrome/test/webdriver/web_element_id.h"
 
 #include "base/logging.h"
 #include "base/values.h"
+#include "chrome/test/automation/javascript_message_utils.h"
 
 namespace {
 
 // Special dictionary key to identify an element ID to WebDriver atoms and
 // remote clients.
 const char kWebElementKey[] = "ELEMENT";
 
 }  // namespace
 
 namespace webdriver {
 
 const char LocatorType::kClassName[] = "className";
 const char LocatorType::kCss[] = "css";
 const char LocatorType::kId[] = "id";
 const char LocatorType::kLinkText[] = "linkText";
 const char LocatorType::kName[] = "name";
 const char LocatorType::kPartialLinkText[] = "partialLinkText";
 const char LocatorType::kTagName[] = "tagName";
 const char LocatorType::kXpath[] = "xpath";
 
 WebElementId::WebElementId() : is_valid_(false) {}
 
 WebElementId::WebElementId(const std::string& id) : id_(id), is_valid_(true) {}
 
-WebElementId::WebElementId(Value* value) {
+WebElementId::WebElementId(const Value* value) {
   is_valid_ = false;
   if (value->IsType(Value::TYPE_DICTIONARY)) {
-    is_valid_ = static_cast<DictionaryValue*>(value)->
+    is_valid_ = static_cast<const DictionaryValue*>(value)->
         GetString(kWebElementKey, &id_);
   }
 }
 
 WebElementId::~WebElementId() {}
 
 Value* WebElementId::ToValue() const {
   CHECK(is_valid_);
   if (id_.empty())
     return Value::CreateNullValue();
   DictionaryValue* element = new DictionaryValue();
   element->SetString(kWebElementKey, id_);
   return element;
 }
 
 bool WebElementId::is_valid() const {
   return is_valid_;
 }
 
 }  // namespace webdriver
+
+base::Value* ValueConversionTraits<webdriver::WebElementId>::CreateValueFrom(
+    const webdriver::WebElementId& t) {
+  return t.ToValue();
+}
+
+bool ValueConversionTraits<webdriver::WebElementId>::SetFromValue(
+    const base::Value* value, webdriver::WebElementId* t) {
+  webdriver::WebElementId id(value);
+  if (id.is_valid())
+    *t = id;
+  return id.is_valid();
+}
+
+bool ValueConversionTraits<webdriver::WebElementId>::CanConvert(
+    const base::Value* value) {
+  webdriver::WebElementId t;
+  return SetFromValue(value, &t);
+}