Bug 1481467 part 1 - Use JSAutoRealm instead of JSAutoRealmAllowCCW in mozJSComponentLoader::ImportInto. r=kmag

The targetVal argument is always same-compartment with the JSContext, so we only need to use JSAutoRealm in the FindTargetObject case.

js/xpconnect/loader/mozJSComponentLoader.cpp

@@ -993,6 +993,8 @@ mozJSComponentLoader::ImportInto(const nsACString& registryLocation,
 
     RootedValue targetVal(cx, targetValArg);
     RootedObject targetObject(cx, nullptr);
+
+    Maybe<JSAutoRealm> ar;
     if (optionalArgc) {
         // The caller passed in the optional second argument. Get it.
         if (targetVal.isObject()) {
@@ -1016,12 +1018,12 @@ mozJSComponentLoader::ImportInto(const nsACString& registryLocation,
         }
     } else {
         FindTargetObject(cx, &targetObject);
+        if (targetObject) {
+            ar.emplace(cx, targetObject);
+        }
     }
 
-    Maybe<JSAutoRealmAllowCCW> ar;
-    if (targetObject) {
-        ar.emplace(cx, targetObject);
-    }
+    js::AssertSameCompartment(cx, targetObject);
 
     RootedObject global(cx);
     nsresult rv = ImportInto(registryLocation, targetObject, cx, &global);