Bug 1839316: part 4) Add RequestPriority to ScriptFetchOptions and ScriptLoadRequest. r=smaug

The request priority isn't propagated from `ScriptFetchOptions`, so
setting it has no effect for end-users. That will be implemented in a
following part.

Differential Revision: https://phabricator.services.mozilla.com/D183483

js/loader/ScriptLoadRequest.cpp

@@ -37,11 +37,13 @@ NS_IMPL_CYCLE_COLLECTION(ScriptFetchOptions, mTriggeringPrincipal, mElement)
 
 ScriptFetchOptions::ScriptFetchOptions(
     mozilla::CORSMode aCORSMode, mozilla::dom::ReferrerPolicy aReferrerPolicy,
-    const nsAString& aNonce, const ParserMetadata aParserMetadata,
-    nsIPrincipal* aTriggeringPrincipal, mozilla::dom::Element* aElement)
+    const nsAString& aNonce, mozilla::dom::RequestPriority aFetchPriority,
+    const ParserMetadata aParserMetadata, nsIPrincipal* aTriggeringPrincipal,
+    mozilla::dom::Element* aElement)
     : mCORSMode(aCORSMode),
       mReferrerPolicy(aReferrerPolicy),
       mNonce(aNonce),
+      mFetchPriority(aFetchPriority),
       mParserMetadata(aParserMetadata),
       mTriggeringPrincipal(aTriggeringPrincipal),
       mElement(aElement) {}