--- a/caps/BasePrincipal.cpp
+++ b/caps/BasePrincipal.cpp
@@ -52,17 +52,17 @@ PrincipalOriginAttributes::InheritFromDo
 }
 
 void
 PrincipalOriginAttributes::InheritFromNecko(const NeckoOriginAttributes& aAttrs)
 {
   mAppId = aAttrs.mAppId;
   mInIsolatedMozBrowser = aAttrs.mInIsolatedMozBrowser;
 
-  // addonId is computed from the principal URI and never propagated
+  mAddonId = aAttrs.mAddonId;
   mUserContextId = aAttrs.mUserContextId;
   mSignedPkg = aAttrs.mSignedPkg;
 
   mPrivateBrowsingId = aAttrs.mPrivateBrowsingId;
   mFirstPartyDomain = aAttrs.mFirstPartyDomain;
 }
 
 void

--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -395,30 +395,16 @@ nsScriptSecurityManager::GetChannelResul
                 principalToInherit.forget(aPrincipal);
                 return NS_OK;
             }
         }
     }
     return GetChannelURIPrincipal(aChannel, aPrincipal);
 }
 
-nsresult
-nsScriptSecurityManager::MaybeSetAddonIdFromURI(PrincipalOriginAttributes& aAttrs, nsIURI* aURI)
-{
-  nsAutoCString scheme;
-  nsresult rv = aURI->GetScheme(scheme);
-  NS_ENSURE_SUCCESS(rv, rv);
-  if (scheme.EqualsLiteral("moz-extension") && GetAddonPolicyService()) {
-    rv = GetAddonPolicyService()->ExtensionURIToAddonId(aURI, aAttrs.mAddonId);
-    NS_ENSURE_SUCCESS(rv, rv);
-  }
-
-  return NS_OK;
-}
-
 /* The principal of the URI that this channel is loading. This is never
  * affected by things like sandboxed loads, or loads where we forcefully
  * inherit the principal.  Think of this as the principal of the server
  * which this channel is loading from.  Most callers should use
  * GetChannelResultPrincipal instead of GetChannelURIPrincipal.  Only
  * call GetChannelURIPrincipal if you are sure that you want the
  * principal that matches the uri, even in cases when the load is
  * sandboxed or when the load could be a blob or data uri (i.e even when
@@ -446,18 +432,17 @@ nsScriptSecurityManager::GetChannelURIPr
     // For subresource loading, the origin attributes of the loadInfo is from
     // its loadingPrincipal.
     PrincipalOriginAttributes attrs;
 
     // For addons loadInfo might be null.
     if (loadInfo) {
       attrs.InheritFromNecko(loadInfo->GetOriginAttributes());
     }
-    rv = MaybeSetAddonIdFromURI(attrs, uri);
-    NS_ENSURE_SUCCESS(rv, rv);
+
     nsCOMPtr<nsIPrincipal> prin = BasePrincipal::CreateCodebasePrincipal(uri, attrs);
     prin.forget(aPrincipal);
     return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
 nsScriptSecurityManager::IsSystemPrincipal(nsIPrincipal* aPrincipal,
                                            bool* aIsSystem)
@@ -1205,33 +1190,29 @@ nsScriptSecurityManager::
 {
   DocShellOriginAttributes docShellAttrs;
   bool result = aLoadContext->GetOriginAttributes(docShellAttrs);;
   NS_ENSURE_TRUE(result, NS_ERROR_FAILURE);
 
   PrincipalOriginAttributes attrs;
   attrs.InheritFromDocShellToDoc(docShellAttrs, aURI);
 
-  nsresult rv = MaybeSetAddonIdFromURI(attrs, aURI);
-  NS_ENSURE_SUCCESS(rv, rv);
   nsCOMPtr<nsIPrincipal> prin = BasePrincipal::CreateCodebasePrincipal(aURI, attrs);
   prin.forget(aPrincipal);
   return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
 nsScriptSecurityManager::GetDocShellCodebasePrincipal(nsIURI* aURI,
                                                       nsIDocShell* aDocShell,
                                                       nsIPrincipal** aPrincipal)
 {
   PrincipalOriginAttributes attrs;
   attrs.InheritFromDocShellToDoc(nsDocShell::Cast(aDocShell)->GetOriginAttributes(), aURI);
 
-  nsresult rv = MaybeSetAddonIdFromURI(attrs, aURI);
-  NS_ENSURE_SUCCESS(rv, rv);
   nsCOMPtr<nsIPrincipal> prin = BasePrincipal::CreateCodebasePrincipal(aURI, attrs);
   prin.forget(aPrincipal);
   return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
 }
 
 // static
 nsIPrincipal*
 nsScriptSecurityManager::doGetObjectPrincipal(JSObject *aObj)

--- a/caps/nsScriptSecurityManager.h
+++ b/caps/nsScriptSecurityManager.h
@@ -108,19 +108,16 @@ private:
     InitPrefs();
 
     inline void
     ScriptSecurityPrefChanged();
 
     inline void
     AddSitesToFileURIWhitelist(const nsCString& aSiteList);
 
-    // If aURI is a moz-extension:// URI, set mAddonId to the associated addon.
-    nsresult MaybeSetAddonIdFromURI(mozilla::PrincipalOriginAttributes& aAttrs, nsIURI* aURI);
-
     nsresult GetChannelResultPrincipal(nsIChannel* aChannel,
                                        nsIPrincipal** aPrincipal,
                                        bool aIgnoreSandboxing);
 
     nsresult
     CheckLoadURIFlags(nsIURI* aSourceURI, nsIURI* aTargetURI, nsIURI* aSourceBaseURI,
                       nsIURI* aTargetBaseURI, uint32_t aFlags);
 
@@ -128,27 +125,16 @@ private:
     bool mPrefInitialized;
     bool mIsJavaScriptEnabled;
     nsTArray<nsCOMPtr<nsIURI>> mFileURIWhitelist;
 
     // This machinery controls new-style domain policies. The old-style
     // policy machinery will be removed soon.
     nsCOMPtr<nsIDomainPolicy> mDomainPolicy;
 
-    // Cached addon policy service. We can't generate this in Init() because
-    // that's too early to get a service.
-    mozilla::Maybe<nsCOMPtr<nsIAddonPolicyService>> mAddonPolicyService;
-    nsIAddonPolicyService* GetAddonPolicyService()
-    {
-        if (mAddonPolicyService.isNothing()) {
-            mAddonPolicyService.emplace(do_GetService("@mozilla.org/addons/policy-service;1"));
-        }
-        return mAddonPolicyService.ref();
-    }
-
     static bool sStrictFileOriginPolicy;
 
     static nsIIOService    *sIOService;
     static nsIStringBundle *sStrBundle;
     static JSContext       *sContext;
 };
 
 namespace mozilla {

--- a/netwerk/protocol/res/ExtensionProtocolHandler.cpp
+++ b/netwerk/protocol/res/ExtensionProtocolHandler.cpp
@@ -112,16 +112,28 @@ ExtensionProtocolHandler::ResolveSpecial
 }
 
 nsresult
 ExtensionProtocolHandler::SubstituteChannel(nsIURI* aURI,
                                             nsILoadInfo* aLoadInfo,
                                             nsIChannel** result)
 {
   nsresult rv;
+
+  // Flag all requests with the addon id in origin attributes.
+  nsCOMPtr<nsIAddonPolicyService> aps =
+    do_GetService("@mozilla.org/addons/policy-service;1");
+  if (aps) {
+    NeckoOriginAttributes nAttrs;
+    aLoadInfo->GetOriginAttributes(&nAttrs);
+    rv = aps->ExtensionURIToAddonId(aURI, nAttrs.mAddonId);
+    NS_ENSURE_SUCCESS(rv, rv);
+    aLoadInfo->SetOriginAttributes(nAttrs);
+  }
+
   nsCOMPtr<nsIURL> url = do_QueryInterface(aURI, &rv);
   NS_ENSURE_SUCCESS(rv, rv);
 
   nsAutoCString ext;
   rv = url->GetFileExtension(ext);
   NS_ENSURE_SUCCESS(rv, rv);
 
   if (!ext.LowerCaseEqualsLiteral("css")) {