Issue #1442 - Part 10c - Use application/octet-stream for arrayBuffer in sendBeacon. https://bugzilla.mozilla.org/show_bug.cgi?id=1329298 Pre-requisite for Part 11.

dom/base/Navigator.h

@@ -256,9 +256,17 @@ private:
   bool CheckPermission(const char* type);
   static bool CheckPermission(nsPIDOMWindowInner* aWindow, const char* aType);
 
+  // This enum helps SendBeaconInternal to apply different behaviors to body
+  // types.
+  enum BeaconType {
+    eBeaconTypeBlob,
+    eBeaconTypeArrayBuffer,
+    eBeaconTypeOther
+  };
+
   bool SendBeaconInternal(const nsAString& aUrl,
                           BodyExtractorBase* aBody,
-                          bool aIsBlob,
+                          BeaconType aType,
                           ErrorResult& aRv);
 
   RefPtr<nsMimeTypeArray> mMimeTypes;