code: private void replaceStringNodeLocationForExportedTopLevelVariable(
        Node n, int sourcePosition, int length) {
      if (n.hasOneChild()) {
        Node assign = n.getFirstChild();
        if (assign != null && assign.isAssign()) {
          // ASSIGN always has two children.
          Node getProp = assign.getFirstChild();
          if (getProp != null && getProp.isGetProp()) {
            // GETPROP always has two children: a name node and a string node. They should both take
            // on the source range of the original variable.
            for (Node child : getProp.children()) {
              child.setSourceEncodedPosition(sourcePosition);
              child.setLength(length);
            }
          }
        }
      }
    }
docs: If we had something like const FOO = "text" and we export FOO, change the source location
  information for the rewritten FOO. The replacement should be something like MOD.FOO = "text",
  so we look for MOD.FOO and replace the source location for FOO to the original location of FOO.
  
  @param n node tree to modify
  @param sourcePosition position to set for the start of the STRING node.
  @param length length to set for STRING node.