add default content type for raw serializer

src/android/com/silkimen/cordovahttp/CordovaHttpBase.java

@@ -143,6 +143,8 @@ abstract class CordovaHttpBase implements Runnable {
       request.contentType("application/json", "UTF-8");
     } else if ("utf8".equals(this.serializer)) {
       request.contentType("text/plain", "UTF-8");
+    } else if ("raw".equals(this.serializer)) {
+      request.contentType("application/octet-stream");
     } else if ("urlencoded".equals(this.serializer)) {
       // intentionally left blank, because content type is set in HttpRequest.form()
     } else if ("multipart".equals(this.serializer)) {

src/ios/BinaryRequestSerializer.m

@@ -29,6 +29,10 @@
     }];
 
     if (parameters) {
+        if (![mutableRequest valueForHTTPHeaderField:@"Content-Type"]) {
+            [mutableRequest setValue:@"application/octet-stream" forHTTPHeaderField:@"Content-Type"];
+        }
+
         [mutableRequest setHTTPBody: parameters];
     }