67797: add Components.isSuccessCode (r=jag, sr=jband)

js/src/xpconnect/idl/xpccomponents.idl

@@ -130,6 +130,7 @@ interface nsIXPCComponents : nsISupports
     readonly attribute nsIXPCComponents_Exception   Exception;
     readonly attribute nsIXPCComponents_Constructor Constructor;
 
+    boolean isSuccessCode(in nsresult result);
     /* 'lastResult' is accessable via JavaScript only */
     /* 'returnCode' is accessable via JavaScript only */
 };

js/src/xpconnect/src/xpccomponents.cpp

@@ -1919,6 +1919,13 @@ XPC_IMPL_GET_OBJ_METHOD(Constructor);
 #undef XPC_IMPL_GET_OBJ_METHOD
 /*******************************************/
 
+NS_IMETHODIMP
+nsXPCComponents::IsSuccessCode(nsresult result, PRBool *out)
+{
+    *out = NS_SUCCEEDED(result);
+    return NS_OK;
+}
+
 NS_IMETHODIMP
 nsXPCComponents::GetStack(nsIJSStackFrameLocation * *aStack)
 {