base: Add AsList() function to Value API.

base/values.cc

Index: base/values.cc
diff --git a/base/values.cc b/base/values.cc
index 799e100ea87b2f4015d9e5eb51dea14c2f04f327..b61e86892e1251285ca8132b3eabe7f722f475b4 100644
--- a/base/values.cc
+++ b/base/values.cc
@@ -100,6 +100,10 @@ StringValue* Value::CreateStringValue(const string16& in_value) {
   return new StringValue(in_value);
 }
 
+ListValue* Value::AsList() {
+  return NULL;
+}
+
 bool Value::GetAsBoolean(bool* out_value) const {
   return false;
 }
@@ -519,7 +523,7 @@ bool DictionaryValue::GetList(const std::string& path,
                               ListValue** out_value) const {
   Value* value;
   bool result = Get(path, &value);
-  if (!result || !value->IsType(TYPE_LIST))
+  if (!result || !value->AsList())
     return false;
 
   if (out_value)
@@ -597,7 +601,7 @@ bool DictionaryValue::GetListWithoutPathExpansion(const std::string& key,
                                                   ListValue** out_value) const {
   Value* value;
   bool result = GetWithoutPathExpansion(key, &value);
-  if (!result || !value->IsType(TYPE_LIST))
+  if (!result || !value->AsList())
     return false;
 
   if (out_value)
@@ -810,7 +814,7 @@ bool ListValue::GetDictionary(size_t index, DictionaryValue** out_value) const {
 bool ListValue::GetList(size_t index, ListValue** out_value) const {
   Value* value;
   bool result = Get(index, &value);
-  if (!result || !value->IsType(TYPE_LIST))
+  if (!result || !value->AsList())
     return false;
 
   if (out_value)
@@ -873,6 +877,10 @@ bool ListValue::Insert(size_t index, Value* in_value) {
   return true;
 }
 
+ListValue* ListValue::AsList() {
+  return this;
+}
+
 bool ListValue::GetAsList(ListValue** out_value) {
   if (out_value)
     *out_value = this;