Bug 1695404 - follow-up: Avoid redundant string copy in Gecko_IsSupportedImageMimeType. r=tnikkel

There's no reason to require a null-terminated string in imgLoader.

Differential Revision: https://phabricator.services.mozilla.com/D112478

dom/html/HTMLImageElement.cpp

@@ -1098,8 +1098,7 @@ bool HTMLImageElement::SupportedPictureSourceType(const nsAString& aType) {
   }
 
   return imgLoader::SupportImageWithMimeType(
-      NS_ConvertUTF16toUTF8(type).get(),
-      AcceptedMimeTypes::IMAGES_AND_DOCUMENTS);
+      NS_ConvertUTF16toUTF8(type), AcceptedMimeTypes::IMAGES_AND_DOCUMENTS);
 }
 
 bool HTMLImageElement::SourceElementMatches(Element* aSourceElement) {