diff --git a/caps/include/nsScriptSecurityManager.h b/caps/include/nsScriptSecurityManager.h
index ce2d8f33d76..fa531a8cdb4 100644
--- a/caps/include/nsScriptSecurityManager.h
+++ b/caps/include/nsScriptSecurityManager.h
@@ -537,32 +537,22 @@ private:
      * has set the "security.xpconnect.plugin.unrestricted" pref to allow
      * anybody to script plugin objects from anywhere.
      *
-     * @param cx The context we're running on.
-     *           NB: If null, "sameOrigin" does not have any effect.
      * @param aObj The nsISupports representation of the object in question
      *             object, possibly null.
-     * @param aJSObject The JSObject representation of the object in question
-     *                  if |cx| is non-null and |aObjectSecurityLevel| is
-     *                  "sameOrigin". If null will be calculated from aObj (if
-     *                  non-null) if and only if aObj is an XPCWrappedJS. The
-     *                  rationale behind this is that if we're creating a JS
-     *                  wrapper for an XPCWrappedJS, this object definitely
-     *                  expects to be exposed to JS.
+     * @param aJSObject The JSObject representation of the object in question.
+     *                  Only used if |aObjectSecurityLevel| is "sameOrigin".
      * @param aSubjectPrincipal The nominal subject principal used when
-     *                          aObjectSecurityLevel is "sameOrigin". If null,
-     *                          this is calculated if it's needed.
+     *                          aObjectSecurityLevel is "sameOrigin".
      * @param aObjectSecurityLevel Can be one of three values:
      *                  - allAccess: Allow access no matter what.
      *                  - noAccess: Deny access no matter what.
-     *                  - sameOrigin: If |cx| is null, behave like noAccess.
-     *                                Otherwise, possibly compute a subject
-     *                                and object principal and return true if
-     *                                and only if the subject has greater than
-     *                                or equal privileges to the object.
+     *                  - sameOrigin: If both a subject principal and JS
+     *                                object have been passed in, returns
+     *                                true if the subject subsumes the object,
+     *                                otherwise, behaves like noAccess.
      */
     nsresult
-    CheckXPCPermissions(JSContext* cx,
-                        nsISupports* aObj, JSObject* aJSObject,
+    CheckXPCPermissions(nsISupports* aObj, JSObject* aJSObject,
                         nsIPrincipal* aSubjectPrincipal,
                         const char* aObjectSecurityLevel);
 
diff --git a/caps/src/nsScriptSecurityManager.cpp b/caps/src/nsScriptSecurityManager.cpp
index 9f63b71ddb4..30277d4c419 100644
--- a/caps/src/nsScriptSecurityManager.cpp
+++ b/caps/src/nsScriptSecurityManager.cpp
@@ -784,7 +784,7 @@ nsScriptSecurityManager::CheckPropertyAccessImpl(PRUint32 aAction,
             }
         }
     }
-    rv = CheckXPCPermissions(cx, aObj, aJSObject, subjectPrincipal,
+    rv = CheckXPCPermissions(aObj, aJSObject, subjectPrincipal,
                              objectSecurityLevel);
 #ifdef DEBUG_CAPS_CheckPropertyAccessImpl
     if(NS_SUCCEEDED(rv))
@@ -2859,7 +2859,7 @@ nsScriptSecurityManager::CanCreateWrapper(JSContext *cx,
     if (checkedComponent)
         checkedComponent->CanCreateWrapper((nsIID *)&aIID, getter_Copies(objectSecurityLevel));
 
-    nsresult rv = CheckXPCPermissions(cx, aObj, nsnull, nsnull, objectSecurityLevel);
+    nsresult rv = CheckXPCPermissions(aObj, nsnull, nsnull, objectSecurityLevel);
     if (NS_FAILED(rv))
     {
         //-- Access denied, report an error
@@ -2970,7 +2970,7 @@ nsScriptSecurityManager::CanCreateInstance(JSContext *cx,
     nsCRT::free(cidStr);
 #endif
 
-    nsresult rv = CheckXPCPermissions(nsnull, nsnull, nsnull, nsnull, nsnull);
+    nsresult rv = CheckXPCPermissions(nsnull, nsnull, nsnull, nsnull);
     if (NS_FAILED(rv))
 #ifdef XPC_IDISPATCH_SUPPORT
     {
@@ -3007,7 +3007,7 @@ nsScriptSecurityManager::CanGetService(JSContext *cx,
     nsCRT::free(cidStr);
 #endif
 
-    nsresult rv = CheckXPCPermissions(nsnull, nsnull, nsnull, nsnull, nsnull);
+    nsresult rv = CheckXPCPermissions(nsnull, nsnull, nsnull, nsnull);
     if (NS_FAILED(rv))
     {
         //-- Access denied, report an error
@@ -3046,8 +3046,7 @@ nsScriptSecurityManager::CanAccess(PRUint32 aAction,
 }
 
 nsresult
-nsScriptSecurityManager::CheckXPCPermissions(JSContext* cx,
-                                             nsISupports* aObj, JSObject* aJSObject,
+nsScriptSecurityManager::CheckXPCPermissions(nsISupports* aObj, JSObject* aJSObject,
                                              nsIPrincipal* aSubjectPrincipal,
                                              const char* aObjectSecurityLevel)
 {
@@ -3061,40 +3060,20 @@ nsScriptSecurityManager::CheckXPCPermissions(JSContext* cx,
     {
         if (PL_strcasecmp(aObjectSecurityLevel, "allAccess") == 0)
             return NS_OK;
-        if (cx && PL_strcasecmp(aObjectSecurityLevel, "sameOrigin") == 0)
+        if (aSubjectPrincipal && aJSObject &&
+            PL_strcasecmp(aObjectSecurityLevel, "sameOrigin") == 0)
         {
-            nsresult rv;
-            if (!aJSObject)
-            {
-                nsCOMPtr<nsIXPConnectWrappedJS> xpcwrappedjs =
-                    do_QueryInterface(aObj);
-                if (xpcwrappedjs)
-                {
-                    rv = xpcwrappedjs->GetJSObject(&aJSObject);
-                    NS_ENSURE_SUCCESS(rv, rv);
-                }
-            }
+            nsIPrincipal* objectPrincipal = doGetObjectPrincipal(aJSObject);
 
-            if (!aSubjectPrincipal)
+            // Only do anything if we have both a subject and object
+            // principal.
+            if (objectPrincipal)
             {
-                // No subject principal passed in. Compute it.
-                aSubjectPrincipal = GetSubjectPrincipal(cx, &rv);
+                PRBool subsumes;
+                nsresult rv = aSubjectPrincipal->Subsumes(objectPrincipal, &subsumes);
                 NS_ENSURE_SUCCESS(rv, rv);
-            }
-            if (aSubjectPrincipal && aJSObject)
-            {
-                nsIPrincipal* objectPrincipal = doGetObjectPrincipal(aJSObject);
-
-                // Only do anything if we have both a subject and object
-                // principal.
-                if (objectPrincipal)
-                {
-                    PRBool subsumes;
-                    rv = aSubjectPrincipal->Subsumes(objectPrincipal, &subsumes);
-                    NS_ENSURE_SUCCESS(rv, rv);
-                    if (subsumes)
-                        return NS_OK;
-                }
+                if (subsumes)
+                    return NS_OK;
             }
         }
         else if (PL_strcasecmp(aObjectSecurityLevel, "noAccess") != 0)