Fetch API: Fix behavior when Request constructor is passed an undefined referrer

third_party/WebKit/Source/modules/fetch/RequestInit.cpp

Index: third_party/WebKit/Source/modules/fetch/RequestInit.cpp
diff --git a/third_party/WebKit/Source/modules/fetch/RequestInit.cpp b/third_party/WebKit/Source/modules/fetch/RequestInit.cpp
index 54a76a215bdb1497bd74102830eef4e701a0dc90..b714c596c7fc652490cc756c2b964539f6a234cd 100644
--- a/third_party/WebKit/Source/modules/fetch/RequestInit.cpp
+++ b/third_party/WebKit/Source/modules/fetch/RequestInit.cpp
@@ -25,6 +25,8 @@
 
 namespace blink {
 
+// TODO(yiyix): Verify if any DictionaryHelper::get should be replaced with
+// DictionaryHelper::getWithUndefinedCheck.
 RequestInit::RequestInit(ExecutionContext* context,
                          const Dictionary& options,
                          ExceptionState& exceptionState)
@@ -45,8 +47,8 @@ RequestInit::RequestInit(ExecutionContext* context,
   areAnyMembersSet |= DictionaryHelper::get(options, "mode", mode);
   areAnyMembersSet |= DictionaryHelper::get(options, "redirect", redirect);
   AtomicString referrerString;
-  bool isReferrerStringSet =
-      DictionaryHelper::get(options, "referrer", referrerString);
+  bool isReferrerStringSet = DictionaryHelper::getWithUndefinedCheck(
+      options, "referrer", referrerString);
   areAnyMembersSet |= isReferrerStringSet;
   areAnyMembersSet |= DictionaryHelper::get(options, "integrity", integrity);
   AtomicString referrerPolicyString;