diff --git a/caps/BasePrincipal.cpp b/caps/BasePrincipal.cpp
index b92ae65cc7b2..e493294136e1 100644
--- a/caps/BasePrincipal.cpp
+++ b/caps/BasePrincipal.cpp
@@ -347,109 +347,6 @@ BasePrincipal::Equals(nsIPrincipal* aOther, bool* aResult) {
   return NS_OK;
 }
 
-NS_IMETHODIMP
-BasePrincipal::EqualsForPermission(nsIPrincipal* aOther, bool aExactHost,
-                                   bool* aResult) {
-  *aResult = false;
-  NS_ENSURE_ARG_POINTER(aOther);
-  NS_ENSURE_ARG_POINTER(aResult);
-
-  // If the principals are equal, then they match.
-  if (FastEquals(aOther)) {
-    *aResult = true;
-    return NS_OK;
-  }
-
-  // If we are matching with an exact host, we're done now - the permissions
-  // don't match otherwise, we need to start comparing subdomains!
-  if (aExactHost) {
-    return NS_OK;
-  }
-
-  // Compare their OriginAttributes
-  const mozilla::OriginAttributes& theirAttrs = aOther->OriginAttributesRef();
-  const mozilla::OriginAttributes& ourAttrs = OriginAttributesRef();
-
-  if (theirAttrs != ourAttrs) {
-    return NS_OK;
-  }
-
-  nsCOMPtr<nsIURI> ourURI;
-  nsresult rv = GetURI(getter_AddRefs(ourURI));
-  NS_ENSURE_SUCCESS(rv, rv);
-  auto* basePrin = BasePrincipal::Cast(aOther);
-  return basePrin->EqualsURIForPermission(ourURI, aResult);
-}
-
-NS_IMETHODIMP
-BasePrincipal::EqualsURIForPermission(nsIURI* aOther, bool* aResult) {
-  *aResult = false;
-  nsCOMPtr<nsIURI> ourURI;
-  nsresult rv = GetURI(getter_AddRefs(ourURI));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  // Compare schemes
-  nsAutoCString otherScheme;
-  rv = aOther->GetScheme(otherScheme);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  nsAutoCString ourScheme;
-  rv = ourURI->GetScheme(ourScheme);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (otherScheme != ourScheme) {
-    return NS_OK;
-  }
-
-  // Compare ports
-  int32_t theirPort;
-  rv = aOther->GetPort(&theirPort);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  int32_t ourPort;
-  rv = ourURI->GetPort(&ourPort);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (theirPort != ourPort) {
-    return NS_OK;
-  }
-
-  // Check if the host or any subdomain of their host matches.
-  nsAutoCString theirHost;
-  rv = aOther->GetHost(theirHost);
-  if (NS_FAILED(rv) || theirHost.IsEmpty()) {
-    return NS_OK;
-  }
-
-  nsAutoCString ourHost;
-  rv = ourURI->GetHost(ourHost);
-  if (NS_FAILED(rv) || ourHost.IsEmpty()) {
-    return NS_OK;
-  }
-
-  nsCOMPtr<nsIEffectiveTLDService> tldService =
-      do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
-  if (!tldService) {
-    NS_ERROR("Should have a tld service!");
-    return NS_ERROR_FAILURE;
-  }
-
-  // This loop will not loop forever, as GetNextSubDomain will eventually fail
-  // with NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS.
-  while (theirHost != ourHost) {
-    rv = tldService->GetNextSubDomain(theirHost, theirHost);
-    if (NS_FAILED(rv)) {
-      if (rv == NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS) {
-        return NS_OK;
-      }
-      return rv;
-    }
-  }
-
-  *aResult = true;
-  return NS_OK;
-}
-
 NS_IMETHODIMP
 BasePrincipal::EqualsConsideringDomain(nsIPrincipal* aOther, bool* aResult) {
   NS_ENSURE_ARG_POINTER(aOther);
diff --git a/caps/BasePrincipal.h b/caps/BasePrincipal.h
index 941751bd0350..4ee0adf60e25 100644
--- a/caps/BasePrincipal.h
+++ b/caps/BasePrincipal.h
@@ -106,9 +106,6 @@ class BasePrincipal : public nsJSPrincipals {
   NS_IMETHOD Equals(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD EqualsConsideringDomain(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD EqualsURI(nsIURI* aOtherURI, bool* _retval) override;
-  NS_IMETHOD EqualsForPermission(nsIPrincipal* other, bool aExactHost,
-                                 bool* _retval) final;
-  NS_IMETHOD EqualsURIForPermission(nsIURI* other, bool* _retval) final;
   NS_IMETHOD Subsumes(nsIPrincipal* other, bool* _retval) final;
   NS_IMETHOD SubsumesConsideringDomain(nsIPrincipal* other,
                                        bool* _retval) final;
diff --git a/caps/nsIPrincipal.idl b/caps/nsIPrincipal.idl
index 674aa253680b..2fb373dc532d 100644
--- a/caps/nsIPrincipal.idl
+++ b/caps/nsIPrincipal.idl
@@ -58,14 +58,6 @@ interface nsIPrincipal : nsISerializable
      */
     boolean equals(in nsIPrincipal other);
 
-    /**
-     * Returns whether the other principal is equivalent to this principal
-     * for permission purposes
-     * Matches {originAttributes ,equalsURIForPermission}
-     */
-
-    boolean equalsForPermission(in nsIPrincipal other, in bool aExactHost);
-
     /**
      * Like equals, but takes document.domain changes into account.
      */
diff --git a/extensions/permissions/Permission.cpp b/extensions/permissions/Permission.cpp
index 19b4ba26f841..47e95b0bac6d 100644
--- a/extensions/permissions/Permission.cpp
+++ b/extensions/permissions/Permission.cpp
@@ -119,8 +119,101 @@ Permission::Matches(nsIPrincipal* aPrincipal, bool aExactHost, bool* aMatches) {
 
 NS_IMETHODIMP
 Permission::MatchesPrincipalForPermission(nsIPrincipal* aPrincipal,
-                                            bool aExactHost, bool* aMatches) {
-  return mPrincipal->EqualsForPermission(aPrincipal, aExactHost, aMatches);
+                                          bool aExactHost, bool* aMatches) {
+  NS_ENSURE_ARG_POINTER(aPrincipal);
+  NS_ENSURE_ARG_POINTER(aMatches);
+
+  *aMatches = false;
+
+  // If the principals are equal, then they match.
+  if (mPrincipal->Equals(aPrincipal)) {
+    *aMatches = true;
+    return NS_OK;
+  }
+
+  // If we are matching with an exact host, we're done now - the permissions
+  // don't match otherwise, we need to start comparing subdomains!
+  if (aExactHost) {
+    return NS_OK;
+  }
+
+  // Compare their OriginAttributes
+  const mozilla::OriginAttributes& theirAttrs =
+      aPrincipal->OriginAttributesRef();
+  const mozilla::OriginAttributes& ourAttrs = mPrincipal->OriginAttributesRef();
+
+  if (theirAttrs != ourAttrs) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> theirURI;
+  nsresult rv = aPrincipal->GetURI(getter_AddRefs(theirURI));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> ourURI;
+  rv = mPrincipal->GetURI(getter_AddRefs(ourURI));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Compare schemes
+  nsAutoCString theirScheme;
+  rv = theirURI->GetScheme(theirScheme);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString ourScheme;
+  rv = ourURI->GetScheme(ourScheme);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (theirScheme != ourScheme) {
+    return NS_OK;
+  }
+
+  // Compare ports
+  int32_t theirPort;
+  rv = theirURI->GetPort(&theirPort);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  int32_t ourPort;
+  rv = ourURI->GetPort(&ourPort);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (theirPort != ourPort) {
+    return NS_OK;
+  }
+
+  // Check if the host or any subdomain of their host matches.
+  nsAutoCString theirHost;
+  rv = theirURI->GetHost(theirHost);
+  if (NS_FAILED(rv) || theirHost.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsAutoCString ourHost;
+  rv = ourURI->GetHost(ourHost);
+  if (NS_FAILED(rv) || ourHost.IsEmpty()) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIEffectiveTLDService> tldService =
+      do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
+  if (!tldService) {
+    NS_ERROR("Should have a tld service!");
+    return NS_ERROR_FAILURE;
+  }
+
+  // This loop will not loop forever, as GetNextSubDomain will eventually fail
+  // with NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS.
+  while (theirHost != ourHost) {
+    rv = tldService->GetNextSubDomain(theirHost, theirHost);
+    if (NS_FAILED(rv)) {
+      if (rv == NS_ERROR_INSUFFICIENT_DOMAIN_LEVELS) {
+        return NS_OK;
+      }
+      return rv;
+    }
+  }
+
+  *aMatches = true;
+  return NS_OK;
 }
 
 NS_IMETHODIMP