Use base::FooValue::From() to simplify gpu code.

gpu/config/gpu_control_list.cc

 // Copyright (c) 2013 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 "gpu/config/gpu_control_list.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
@@ skipping 1376 matching lines @@
       control_list_logging_enabled_(false) {
 }
 
 GpuControlList::~GpuControlList() {
   Clear();
 }
 
 bool GpuControlList::LoadList(
     const std::string& json_context,
     GpuControlList::OsFilter os_filter) {
-  std::unique_ptr<base::Value> root = base::JSONReader::Read(json_context);
-  if (root.get() == NULL || !root->IsType(base::Value::TYPE_DICTIONARY))
+  std::unique_ptr<base::DictionaryValue> root =
+      base::DictionaryValue::From(base::JSONReader::Read(json_context));
+  if (!root)
     return false;
-
-  base::DictionaryValue* root_dictionary =
-      static_cast<base::DictionaryValue*>(root.get());
-  DCHECK(root_dictionary);
-  return LoadList(*root_dictionary, os_filter);
+  return LoadList(*root, os_filter);
 }
 
 bool GpuControlList::LoadList(const base::DictionaryValue& parsed_json,
                               GpuControlList::OsFilter os_filter) {
   std::vector<ScopedGpuControlListEntry> entries;
 
   parsed_json.GetString("version", &version_);
   std::vector<std::string> pieces;
   if (!ProcessVersionString(version_, '.', &pieces))
     return false;
@@ skipping 201 matching lines @@
     const std::string& feature_name, int feature_id) {
   feature_map_[feature_name] = feature_id;
 }
 
 void GpuControlList::set_supports_feature_type_all(bool supported) {
   supports_feature_type_all_ = supported;
 }
 
 }  // namespace gpu