--- a/caps/BasePrincipal.cpp
+++ b/caps/BasePrincipal.cpp
@@ -2,17 +2,16 @@
 /* vim: set ts=2 sw=2 et tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/BasePrincipal.h"
 
 #include "nsDocShell.h"
-#include "nsIAddonPolicyService.h"
 #include "nsIContentSecurityPolicy.h"
 #include "nsIObjectInputStream.h"
 #include "nsIObjectOutputStream.h"
 #include "nsIStandardURL.h"
 
 #include "ContentPrincipal.h"
 #include "nsNetUtil.h"
 #include "nsIURIWithPrincipal.h"
@@ -326,34 +325,40 @@ BasePrincipal::GetPrivateBrowsingId(uint
 
 NS_IMETHODIMP
 BasePrincipal::GetIsInIsolatedMozBrowserElement(bool* aIsInIsolatedMozBrowserElement)
 {
   *aIsInIsolatedMozBrowserElement = IsInIsolatedMozBrowserElement();
   return NS_OK;
 }
 
+nsresult
+BasePrincipal::GetAddonPolicy(nsISupports** aResult)
+{
+  *aResult = AddonPolicy();
+  return NS_OK;
+}
+
+extensions::WebExtensionPolicy*
+BasePrincipal::AddonPolicy()
+{
+  if (Is<ContentPrincipal>()) {
+    return As<ContentPrincipal>()->AddonPolicy();
+  }
+  return nullptr;
+}
+
 bool
 BasePrincipal::AddonHasPermission(const nsAString& aPerm)
 {
-  nsAutoString addonId;
-  NS_ENSURE_SUCCESS(GetAddonId(addonId), false);
-
-  if (addonId.IsEmpty()) {
-    return false;
+  auto policy = AddonPolicy();
+  if (policy) {
+    return policy->HasPermission(aPerm);
   }
-
-  nsCOMPtr<nsIAddonPolicyService> aps =
-    do_GetService("@mozilla.org/addons/policy-service;1");
-  NS_ENSURE_TRUE(aps, false);
-
-  bool retval = false;
-  nsresult rv = aps->AddonHasPermission(addonId, aPerm, &retval);
-  NS_ENSURE_SUCCESS(rv, false);
-  return retval;
+  return false;
 }
 
 already_AddRefed<BasePrincipal>
 BasePrincipal::CreateCodebasePrincipal(nsIURI* aURI,
                                        const OriginAttributes& aAttrs)
 {
   MOZ_ASSERT(aURI);
 
@@ -443,29 +448,21 @@ BasePrincipal::CloneStrippingUserContext
   NS_ENSURE_SUCCESS(rv, nullptr);
 
   return BasePrincipal::CreateCodebasePrincipal(uri, attrs);
 }
 
 bool
 BasePrincipal::AddonAllowsLoad(nsIURI* aURI, bool aExplicit /* = false */)
 {
-  nsAutoString addonId;
-  NS_ENSURE_SUCCESS(GetAddonId(addonId), false);
-
-  if (addonId.IsEmpty()) {
-    return false;
+  auto policy = AddonPolicy();
+  if (policy) {
+    return policy->CanAccessURI(aURI, aExplicit);
   }
-
-  nsCOMPtr<nsIAddonPolicyService> aps = do_GetService("@mozilla.org/addons/policy-service;1");
-  NS_ENSURE_TRUE(aps, false);
-
-  bool allowed = false;
-  nsresult rv = aps->AddonMayLoadURI(addonId, aURI, aExplicit, &allowed);
-  return NS_SUCCEEDED(rv) && allowed;
+  return false;
 }
 
 void
 BasePrincipal::FinishInit(const nsACString& aOriginNoSuffix,
                           const OriginAttributes& aOriginAttributes)
 {
   mInitialized = true;
   mOriginAttributes = aOriginAttributes;

--- a/caps/BasePrincipal.h
+++ b/caps/BasePrincipal.h
@@ -59,16 +59,17 @@ public:
   NS_IMETHOD GetOrigin(nsACString& aOrigin) final;
   NS_IMETHOD GetOriginNoSuffix(nsACString& aOrigin) final;
   NS_IMETHOD Equals(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD EqualsConsideringDomain(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD Subsumes(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD SubsumesConsideringDomain(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD SubsumesConsideringDomainIgnoringFPD(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD CheckMayLoad(nsIURI* uri, bool report, bool allowIfInheritsPrincipal) final;
+  NS_IMETHOD GetAddonPolicy(nsISupports** aResult) final;
   NS_IMETHOD GetCsp(nsIContentSecurityPolicy** aCsp) override;
   NS_IMETHOD SetCsp(nsIContentSecurityPolicy* aCsp) override;
   NS_IMETHOD EnsureCSP(nsIDOMDocument* aDocument, nsIContentSecurityPolicy** aCSP) override;
   NS_IMETHOD GetPreloadCsp(nsIContentSecurityPolicy** aPreloadCSP) override;
   NS_IMETHOD EnsurePreloadCSP(nsIDOMDocument* aDocument, nsIContentSecurityPolicy** aCSP) override;
   NS_IMETHOD GetCspJSON(nsAString& outCSPinJSON) override;
   NS_IMETHOD GetIsNullPrincipal(bool* aResult) override;
   NS_IMETHOD GetIsCodebasePrincipal(bool* aResult) override;
@@ -94,16 +95,17 @@ public:
   // not possible to generate a correct origin from the passed URI. If this
   // happens, a NullPrincipal is returned.
 
   static already_AddRefed<BasePrincipal>
   CreateCodebasePrincipal(nsIURI* aURI, const OriginAttributes& aAttrs);
 
   const OriginAttributes& OriginAttributesRef() final { return mOriginAttributes; }
   uint32_t AppId() const { return mOriginAttributes.mAppId; }
+  extensions::WebExtensionPolicy* AddonPolicy();
   uint32_t UserContextId() const { return mOriginAttributes.mUserContextId; }
   uint32_t PrivateBrowsingId() const { return mOriginAttributes.mPrivateBrowsingId; }
   bool IsInIsolatedMozBrowserElement() const { return mOriginAttributes.mInIsolatedMozBrowser; }
 
   PrincipalKind Kind() const { return mKind; }
 
   already_AddRefed<BasePrincipal> CloneStrippingUserContextIdAndFirstPartyDomain();
 

--- a/caps/ContentPrincipal.cpp
+++ b/caps/ContentPrincipal.cpp
@@ -25,16 +25,17 @@
 #include "nsError.h"
 #include "nsIContentSecurityPolicy.h"
 #include "nsNetCID.h"
 #include "jswrapper.h"
 
 #include "mozilla/dom/nsCSPContext.h"
 #include "mozilla/dom/ScriptSettings.h"
 #include "mozilla/ClearOnShutdown.h"
+#include "mozilla/ExtensionPolicyService.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/HashFunctions.h"
 
 using namespace mozilla;
 
 static bool gCodeBasePrincipalSupport = false;
 
 static bool URIIsImmutable(nsIURI* aURI)
@@ -42,27 +43,20 @@ static bool URIIsImmutable(nsIURI* aURI)
   nsCOMPtr<nsIMutable> mutableObj(do_QueryInterface(aURI));
   bool isMutable;
   return
     mutableObj &&
     NS_SUCCEEDED(mutableObj->GetMutable(&isMutable)) &&
     !isMutable;
 }
 
-static nsIAddonPolicyService*
-GetAddonPolicyService(nsresult* aRv)
+static inline ExtensionPolicyService&
+EPS()
 {
-  static nsCOMPtr<nsIAddonPolicyService> addonPolicyService;
-
-  *aRv = NS_OK;
-  if (!addonPolicyService) {
-    addonPolicyService = do_GetService("@mozilla.org/addons/policy-service;1", aRv);
-    ClearOnShutdown(&addonPolicyService);
-  }
-  return addonPolicyService;
+  return ExtensionPolicyService::GetSingleton();
 }
 
 NS_IMPL_CLASSINFO(ContentPrincipal, nullptr, nsIClassInfo::MAIN_THREAD_ONLY,
                   NS_PRINCIPAL_CID)
 NS_IMPL_QUERY_INTERFACE_CI(ContentPrincipal,
                            nsIPrincipal,
                            nsISerializable)
 NS_IMPL_CI_INTERFACE_GETTER(ContentPrincipal,
@@ -420,44 +414,44 @@ ContentPrincipal::GetBaseDomain(nsACStri
     do_GetService(THIRDPARTYUTIL_CONTRACTID);
   if (thirdPartyUtil) {
     return thirdPartyUtil->GetBaseDomain(mCodebase, aBaseDomain);
   }
 
   return NS_OK;
 }
 
+WebExtensionPolicy*
+ContentPrincipal::AddonPolicy()
+{
+  if (!mAddon.isSome()) {
+    NS_ENSURE_TRUE(mCodebase, nullptr);
+
+    bool isMozExt;
+    if (NS_SUCCEEDED(mCodebase->SchemeIs("moz-extension", &isMozExt)) && isMozExt) {
+      mAddon.emplace(EPS().GetByURL(mCodebase.get()));
+    } else {
+      mAddon.emplace(nullptr);
+    }
+  }
+
+  return mAddon.value();
+}
+
 NS_IMETHODIMP
 ContentPrincipal::GetAddonId(nsAString& aAddonId)
 {
-  if (mAddonIdCache.isSome()) {
-    aAddonId.Assign(mAddonIdCache.ref());
-    return NS_OK;
+  auto policy = AddonPolicy();
+  if (policy) {
+    policy->GetId(aAddonId);
+  } else {
+    aAddonId.Truncate();
   }
-
-  NS_ENSURE_TRUE(mCodebase, NS_ERROR_FAILURE);
-
-  nsresult rv;
-  bool isMozExt;
-  if (NS_SUCCEEDED(mCodebase->SchemeIs("moz-extension", &isMozExt)) && isMozExt) {
-    nsIAddonPolicyService* addonPolicyService = GetAddonPolicyService(&rv);
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    nsAutoString addonId;
-    rv = addonPolicyService->ExtensionURIToAddonId(mCodebase, addonId);
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    mAddonIdCache.emplace(addonId);
-  } else {
-    mAddonIdCache.emplace();
-  }
-
-  aAddonId.Assign(mAddonIdCache.ref());
   return NS_OK;
-};
+}
 
 NS_IMETHODIMP
 ContentPrincipal::Read(nsIObjectInputStream* aStream)
 {
   nsCOMPtr<nsISupports> supports;
   nsCOMPtr<nsIURI> codebase;
   nsresult rv = NS_ReadOptionalObject(aStream, true, getter_AddRefs(supports));
   if (NS_FAILED(rv)) {

--- a/caps/ContentPrincipal.h
+++ b/caps/ContentPrincipal.h
@@ -9,16 +9,17 @@
 #include "nsCOMPtr.h"
 #include "nsJSPrincipals.h"
 #include "nsTArray.h"
 #include "nsIContentSecurityPolicy.h"
 #include "nsIProtocolHandler.h"
 #include "nsNetUtil.h"
 #include "nsScriptSecurityManager.h"
 #include "mozilla/BasePrincipal.h"
+#include "mozilla/extensions/WebExtensionPolicy.h"
 
 class ContentPrincipal final : public mozilla::BasePrincipal
 {
 public:
   NS_DECL_NSISERIALIZABLE
   NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
   NS_IMETHOD GetHashValue(uint32_t* aHashValue) override;
   NS_IMETHOD GetURI(nsIURI** aURI) override;
@@ -42,31 +43,33 @@ public:
   /**
    * Called at startup to setup static data, e.g. about:config pref-observers.
    */
   static void InitializeStatics();
 
   static nsresult
   GenerateOriginNoSuffixFromURI(nsIURI* aURI, nsACString& aOrigin);
 
+  mozilla::extensions::WebExtensionPolicy* AddonPolicy();
+
   nsCOMPtr<nsIURI> mDomain;
   nsCOMPtr<nsIURI> mCodebase;
   // If mCodebaseImmutable is true, mCodebase is non-null and immutable
   bool mCodebaseImmutable;
   bool mDomainImmutable;
 
 protected:
   virtual ~ContentPrincipal();
 
   bool SubsumesInternal(nsIPrincipal* aOther,
                         DocumentDomainConsideration aConsideration) override;
   bool MayLoadInternal(nsIURI* aURI) override;
 
 private:
-  mozilla::Maybe<nsString> mAddonIdCache;
+  mozilla::Maybe<mozilla::WeakPtr<mozilla::extensions::WebExtensionPolicy>> mAddon;
 };
 
 #define NS_PRINCIPAL_CONTRACTID "@mozilla.org/principal;1"
 #define NS_PRINCIPAL_CID \
 { 0x653e0e4d, 0x3ee4, 0x45fa, \
   { 0xb2, 0x72, 0x97, 0xc2, 0x0b, 0xc0, 0x1e, 0xb8 } }
 
 #endif // ContentPrincipal_h

--- a/caps/nsIPrincipal.idl
+++ b/caps/nsIPrincipal.idl
@@ -9,16 +9,19 @@
 
 %{C++
 struct JSPrincipals;
 #include "nsCOMPtr.h"
 #include "nsTArray.h"
 #include "mozilla/DebugOnly.h"
 namespace mozilla {
 class OriginAttributes;
+namespace extensions {
+class WebExtensionPolicy;
+}
 }
 
 /**
  * Some methods have a fast path for the case when we're comparing a principal
  * to itself. The situation may happen for example with about:blank documents.
  */
 
 #define DECL_FAST_INLINE_HELPER(method_)                       \
@@ -269,16 +272,18 @@ interface nsIPrincipal : nsISerializable
      */
     [infallible] readonly attribute unsigned long appId;
 
     /**
      * Gets the ID of the add-on this principal belongs to.
      */
     readonly attribute AString addonId;
 
+    readonly attribute nsISupports addonPolicy;
+
     /**
      * Gets the id of the user context this principal is inside.  If this
      * principal is inside the default userContext, this returns
      * nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID.
      */
     [infallible] readonly attribute unsigned long userContextId;
 
     /**

--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -764,23 +764,18 @@ nsScriptSecurityManager::CheckLoadURIWit
     }
 
     // Check for webextension
     rv = NS_URIChainHasFlags(aTargetURI,
                              nsIProtocolHandler::URI_LOADABLE_BY_EXTENSIONS,
                              &hasFlags);
     NS_ENSURE_SUCCESS(rv, rv);
 
-    if (hasFlags) {
-      nsString addonId;
-      aPrincipal->GetAddonId(addonId);
-
-      if (!addonId.IsEmpty()) {
-        return NS_OK;
-      }
+    if (hasFlags && BasePrincipal::Cast(aPrincipal)->AddonPolicy()) {
+      return NS_OK;
     }
 
     // If we get here, check all the schemes can link to each other, from the top down:
     nsCaseInsensitiveCStringComparator stringComparator;
     nsCOMPtr<nsIURI> currentURI = sourceURI;
     nsCOMPtr<nsIURI> currentOtherURI = aTargetURI;
 
     bool denySameSchemeLinks = false;

--- a/caps/nsScriptSecurityManager.h
+++ b/caps/nsScriptSecurityManager.h
@@ -4,19 +4,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef nsScriptSecurityManager_h__
 #define nsScriptSecurityManager_h__
 
 #include "nsIScriptSecurityManager.h"
 
-#include "nsIAddonPolicyService.h"
 #include "mozilla/Maybe.h"
-#include "nsIAddonPolicyService.h"
 #include "nsIPrincipal.h"
 #include "nsCOMPtr.h"
 #include "nsIObserver.h"
 #include "nsServiceManagerUtils.h"
 #include "nsStringFwd.h"
 #include "plstr.h"
 #include "js/TypeDecls.h"
 
@@ -131,27 +129,16 @@ private:
     // access to file: URIs.  Lazily initialized; isNothing() when not yet
     // initialized.
     mozilla::Maybe<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;
 };
 
 #endif // nsScriptSecurityManager_h__

--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -204,17 +204,16 @@
 #include "mozilla/dom/TouchEvent.h"
 
 #include "mozilla/Preferences.h"
 
 #include "imgILoader.h"
 #include "imgRequestProxy.h"
 #include "nsWrapperCacheInlines.h"
 #include "nsSandboxFlags.h"
-#include "nsIAddonPolicyService.h"
 #include "mozilla/dom/AnimatableBinding.h"
 #include "mozilla/dom/AnonymousContent.h"
 #include "mozilla/dom/BindingUtils.h"
 #include "mozilla/dom/DocumentFragment.h"
 #include "mozilla/dom/DocumentTimeline.h"
 #include "mozilla/dom/Event.h"
 #include "mozilla/dom/HTMLBodyElement.h"
 #include "mozilla/dom/HTMLInputElement.h"
@@ -222,16 +221,17 @@
 #include "mozilla/dom/MediaQueryList.h"
 #include "mozilla/dom/NodeFilterBinding.h"
 #include "mozilla/OwningNonNull.h"
 #include "mozilla/dom/TabChild.h"
 #include "mozilla/dom/WebComponentsBinding.h"
 #include "mozilla/dom/CustomElementRegistryBinding.h"
 #include "mozilla/dom/CustomElementRegistry.h"
 #include "mozilla/dom/TimeoutManager.h"
+#include "mozilla/ExtensionPolicyService.h"
 #include "nsFrame.h"
 #include "nsDOMCaretPosition.h"
 #include "nsIDOMHTMLTextAreaElement.h"
 #include "nsViewportInfo.h"
 #include "mozilla/StaticPtr.h"
 #include "nsITextControlElement.h"
 #include "nsIDOMNSEditableElement.h"
 #include "nsIEditor.h"
@@ -2867,30 +2867,28 @@ nsDocument::InitCSP(nsIChannel* aChannel
     Unused << httpChannel->GetResponseHeader(
         NS_LITERAL_CSTRING("content-security-policy-report-only"),
         tCspROHeaderValue);
   }
   NS_ConvertASCIItoUTF16 cspHeaderValue(tCspHeaderValue);
   NS_ConvertASCIItoUTF16 cspROHeaderValue(tCspROHeaderValue);
 
   // Check if this is a document from a WebExtension.
-  nsString addonId;
   nsCOMPtr<nsIPrincipal> principal = NodePrincipal();
-  principal->GetAddonId(addonId);
-  bool applyAddonCSP = !addonId.IsEmpty();
+  auto addonPolicy = BasePrincipal::Cast(principal)->AddonPolicy();
 
   // Check if this is a signed content to apply default CSP.
   bool applySignedContentCSP = false;
   nsCOMPtr<nsILoadInfo> loadInfo = aChannel->GetLoadInfo();
   if (loadInfo && loadInfo->GetVerifySignedContent()) {
     applySignedContentCSP = true;
   }
 
   // If there's no CSP to apply, go ahead and return early
-  if (!applyAddonCSP &&
+  if (!addonPolicy &&
       !applySignedContentCSP &&
       cspHeaderValue.IsEmpty() &&
       cspROHeaderValue.IsEmpty()) {
     if (MOZ_LOG_TEST(gCspPRLog, LogLevel::Debug)) {
       nsCOMPtr<nsIURI> chanURI;
       aChannel->GetURI(getter_AddRefs(chanURI));
       nsAutoCString aspec;
       chanURI->GetAsciiSpec(aspec);
@@ -2904,29 +2902,24 @@ nsDocument::InitCSP(nsIChannel* aChannel
 
   MOZ_LOG(gCspPRLog, LogLevel::Debug, ("Document is an add-on or CSP header specified %p", this));
 
   nsCOMPtr<nsIContentSecurityPolicy> csp;
   rv = principal->EnsureCSP(this, getter_AddRefs(csp));
   NS_ENSURE_SUCCESS(rv, rv);
 
   // ----- if the doc is an addon, apply its CSP.
-  if (applyAddonCSP) {
+  if (addonPolicy) {
     nsCOMPtr<nsIAddonPolicyService> aps = do_GetService("@mozilla.org/addons/policy-service;1");
 
     nsAutoString addonCSP;
-    rv = aps->GetBaseCSP(addonCSP);
-    if (NS_SUCCEEDED(rv)) {
-      csp->AppendPolicy(addonCSP, false, false);
-    }
-
-    rv = aps->GetAddonCSP(addonId, addonCSP);
-    if (NS_SUCCEEDED(rv)) {
-      csp->AppendPolicy(addonCSP, false, false);
-    }
+    Unused << ExtensionPolicyService::GetSingleton().GetBaseCSP(addonCSP);
+    csp->AppendPolicy(addonCSP, false, false);
+
+    csp->AppendPolicy(addonPolicy->ContentSecurityPolicy(), false, false);
   }
 
   // ----- if the doc is a signed content, apply the default CSP.
   // Note that when the content signing becomes a standard, we might have
   // to restrict this enforcement to "remote content" only.
   if (applySignedContentCSP) {
     nsAutoString signedContentCSP;
     Preferences::GetString("security.signed_content.CSP.default",

--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -3338,19 +3338,18 @@ nsGlobalWindow::SetNewDocument(nsIDocume
     // doesn't have one).
     newInnerWindow->mChromeEventHandler = mChromeEventHandler;
   }
 
   // Ask the JS engine to assert that it's valid to access our DocGroup whenever
   // it runs JS code for this compartment. We skip the check if this window is
   // for chrome JS or an add-on.
   nsCOMPtr<nsIPrincipal> principal = mDoc->NodePrincipal();
-  nsString addonId;
-  principal->GetAddonId(addonId);
-  if (GetDocGroup() && !nsContentUtils::IsSystemPrincipal(principal) && addonId.IsEmpty()) {
+  if (GetDocGroup() && !nsContentUtils::IsSystemPrincipal(principal) &&
+      !BasePrincipal::Cast(principal)->AddonPolicy()) {
     js::SetCompartmentValidAccessPtr(cx, newInnerGlobal,
                                      newInnerWindow->GetDocGroup()->GetValidAccessPtr());
   }
 
   kungFuDeathGrip->DidInitializeContext();
 
   // We wait to fire the debugger hook until the window is all set up and hooked
   // up with the outer. See bug 969156.
@@ -9785,18 +9784,17 @@ public:
           NS_ENSURE_TRUE(currentInner, NS_OK);
 
           AutoSafeJSContext cx;
           JS::Rooted<JSObject*> obj(cx, currentInner->FastGetGlobalJSObject());
           if (obj && !js::IsSystemCompartment(js::GetObjectCompartment(obj))) {
             JSCompartment* cpt = js::GetObjectCompartment(obj);
             nsCOMPtr<nsIPrincipal> pc = nsJSPrincipals::get(JS_GetCompartmentPrincipals(cpt));
 
-            nsAutoString addonId;
-            if (NS_SUCCEEDED(pc->GetAddonId(addonId)) && !addonId.IsEmpty()) {
+            if (BasePrincipal::Cast(pc)->AddonPolicy()) {
               // We want to nuke all references to the add-on compartment.
               xpc::NukeAllWrappersForCompartment(cx, cpt,
                                                  win->IsInnerWindow() ? js::DontNukeWindowReferences
                                                                       : js::NukeWindowReferences);
             } else {
               // We only want to nuke wrappers for the chrome->content case
               js::NukeCrossCompartmentWrappers(cx, BrowserCompartmentMatcher(), cpt,
                                                win->IsInnerWindow() ? js::DontNukeWindowReferences

--- a/js/xpconnect/src/XPCJSContext.cpp
+++ b/js/xpconnect/src/XPCJSContext.cpp
@@ -554,18 +554,17 @@ XPCJSContext::ActivityCallback(void* arg
 
     XPCJSContext* self = static_cast<XPCJSContext*>(arg);
     self->mWatchdogManager->RecordContextActivity(self, active);
 }
 
 static inline bool
 IsWebExtensionPrincipal(nsIPrincipal* principal, nsAString& addonId)
 {
-    return (NS_SUCCEEDED(principal->GetAddonId(addonId)) &&
-            !addonId.IsEmpty());
+    return BasePrincipal::Cast(principal)->AddonPolicy();
 }
 
 static bool
 IsWebExtensionContentScript(BasePrincipal* principal, nsAString& addonId)
 {
     if (!principal->Is<ExpandedPrincipal>()) {
         return false;
     }

--- a/toolkit/components/extensions/ExtensionPolicyService.cpp
+++ b/toolkit/components/extensions/ExtensionPolicyService.cpp
@@ -245,20 +245,17 @@ ExtensionPolicyService::CheckDocument(ns
   nsCOMPtr<nsPIDOMWindowOuter> win = aDocument->GetWindow();
   if (win) {
     if (win->GetDocumentURI()) {
       CheckContentScripts(win.get(), false);
     }
 
     nsIPrincipal* principal = aDocument->NodePrincipal();
 
-    nsAutoString addonId;
-    Unused << principal->GetAddonId(addonId);
-
-    RefPtr<WebExtensionPolicy> policy = GetByID(addonId);
+    RefPtr<WebExtensionPolicy> policy = BasePrincipal::Cast(principal)->AddonPolicy();
     if (policy) {
       nsCOMPtr<nsIDOMDocument> doc = do_QueryInterface(aDocument);
       ProcessScript().InitExtensionDocument(policy, doc);
     }
   }
 }
 
 // Checks for loads of about:blank into new window globals, and loads any