2 files changed, 5 insertions, 12 deletions
diff --git a/browser/components/feeds/nsFeedSniffer.cpp b/browser/components/feeds/nsFeedSniffer.cpp
index f2d0da776..f314d3d3b 100644
--- a/browser/components/feeds/nsFeedSniffer.cpp
+++ b/browser/components/feeds/nsFeedSniffer.cpp
@@ -185,15 +185,9 @@ IsDocumentElement(const char *start, const char* end)
 static bool
 ContainsTopLevelSubstring(nsACString& dataString, const char *substring) 
 {
-  nsACString::const_iterator start, end;
-  dataString.BeginReading(start);
-  dataString.EndReading(end);
-
-  if (!FindInReadable(nsCString(substring), start, end)){
+  int32_t offset = dataString.Find(substring);
+  if (offset == -1)
     return false;
-  }
-
-  auto offset = start.get() - dataString.Data();
 
   const char *begin = dataString.BeginReading();
 
@@ -318,10 +312,9 @@ nsFeedSniffer::GetMIMETypeFromContent(nsIRequest* request,
 
   // RSS 1.0
   if (!isFeed) {
-    bool foundNS_RDF = FindInReadable(NS_LITERAL_CSTRING(NS_RDF), dataString);
-    bool foundNS_RSS = FindInReadable(NS_LITERAL_CSTRING(NS_RSS), dataString);
     isFeed = ContainsTopLevelSubstring(dataString, "<rdf:RDF") &&
-      foundNS_RDF && foundNS_RSS;
+      dataString.Find(NS_RDF) != -1 &&
+      dataString.Find(NS_RSS) != -1;
   }
 
   // If we sniffed a feed, coerce our internal type
diff --git a/browser/components/feeds/nsFeedSniffer.h b/browser/components/feeds/nsFeedSniffer.h
index b7ac002bd..a0eb9862c 100644
--- a/browser/components/feeds/nsFeedSniffer.h
+++ b/browser/components/feeds/nsFeedSniffer.h
@@ -6,7 +6,7 @@
 
 #include "nsIContentSniffer.h"
 #include "nsIStreamListener.h"
-#include "nsString.h"
+#include "nsStringAPI.h"
 #include "mozilla/Attributes.h"
 
 class nsFeedSniffer final : public nsIContentSniffer,