Remove use of deprecated base::ListValue::Append(Value*) overload in extensions.

extensions/browser/api/web_request/web_request_api_helpers.cc

Index: extensions/browser/api/web_request/web_request_api_helpers.cc
diff --git a/extensions/browser/api/web_request/web_request_api_helpers.cc b/extensions/browser/api/web_request/web_request_api_helpers.cc
index a4895d7d401f80bd7a67f6f2ea38c14205577f97..097d3a3a0e0fac9de7e6fb5dad7fd40271180bf0 100644
--- a/extensions/browser/api/web_request/web_request_api_helpers.cc
+++ b/extensions/browser/api/web_request/web_request_api_helpers.cc
@@ -1275,10 +1275,11 @@ void SendExtensionWebRequestStatusToHost(content::RenderProcessHost* host) {
 }
 
 // Converts the |name|, |value| pair of a http header to a HttpHeaders
-// dictionary. Ownership is passed to the caller.
-base::DictionaryValue* CreateHeaderDictionary(
-    const std::string& name, const std::string& value) {
-  base::DictionaryValue* header = new base::DictionaryValue();
+// dictionary.
+std::unique_ptr<base::DictionaryValue> CreateHeaderDictionary(
+    const std::string& name,
+    const std::string& value) {
+  std::unique_ptr<base::DictionaryValue> header(new base::DictionaryValue());
   header->SetString(keys::kHeaderNameKey, name);
   if (base::IsStringUTF8(value)) {
     header->SetString(keys::kHeaderValueKey, value);