--- a/dom/base/nsContentTypeParser.h
+++ b/dom/base/nsContentTypeParser.h
@@ -11,18 +11,18 @@
 
 class nsIMIMEHeaderParam;
 
 class nsContentTypeParser {
 public:
   explicit nsContentTypeParser(const nsAString& aString);
   ~nsContentTypeParser();
 
-  nsresult GetParameter(const char* aParameterName, nsAString& aResult);
-  nsresult GetType(nsAString& aResult);
+  nsresult GetParameter(const char* aParameterName, nsAString& aResult) const;
+  nsresult GetType(nsAString& aResult) const;
 
 private:
   NS_ConvertUTF16toUTF8 mString;
   nsIMIMEHeaderParam*   mService;
 };
 
 #endif
 

--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -6123,26 +6123,27 @@ nsContentTypeParser::nsContentTypeParser
 }
 
 nsContentTypeParser::~nsContentTypeParser()
 {
   NS_IF_RELEASE(mService);
 }
 
 nsresult
-nsContentTypeParser::GetParameter(const char* aParameterName, nsAString& aResult)
+nsContentTypeParser::GetParameter(const char* aParameterName,
+                                  nsAString& aResult) const
 {
   NS_ENSURE_TRUE(mService, NS_ERROR_FAILURE);
   return mService->GetParameterHTTP(mString, aParameterName,
                                     EmptyCString(), false, nullptr,
                                     aResult);
 }
 
 nsresult
-nsContentTypeParser::GetType(nsAString& aResult)
+nsContentTypeParser::GetType(nsAString& aResult) const
 {
   nsresult rv = GetParameter(nullptr, aResult);
   NS_ENSURE_SUCCESS(rv, rv);
   nsContentUtils::ASCIIToLower(aResult);
   return NS_OK;
 }
 
 /* static */