KT-962: Function is called two times

safecall expression now compute receiver only once.

js/src/com/google/dart/compiler/util/AstUtil.java

@@ -309,6 +309,28 @@ public class AstUtil {
         throw new AssertionError("Set qualifier should be applied only to JsInvocation or JsNameRef instances");
     }
 
+    public static JsExpression getQualifier(JsExpression expression) {
+        if (expression instanceof JsInvocation) {
+            return ((JsInvocation) expression).getQualifier();
+        }
+        if (expression instanceof JsNameRef) {
+            return ((JsNameRef) expression).getQualifier();
+        }
+        throw new AssertionError("Get qualifier should be applied only to JsInvocation or JsNameRef instances");
+    }
+
+    public static void substituteTopLevelQualifier(JsExpression expression, JsExpression substitutor) {
+        assert expression != null;
+        JsExpression previous = expression;
+        JsExpression current = getQualifier(expression);
+        assert current != null : "Cannot be applied to unqualified expression";
+        while (getQualifier(current) != null) {
+            previous = current;
+            current = getQualifier(current);
+        }
+        setQualifier(previous, substitutor);
+    }
+
     //TODO: look for should-be-usages
     public static JsNameRef qualified(JsName selector, JsExpression qualifier) {
         JsNameRef reference = selector.makeRef();