As I tried, the `sources` part here does not take any effect. The key part to make this dependency work is the 
```
'variables': { 
  'additional_input_paths': [ 
    '<(PRODUCT_DIR)/xwalk_runtime_lib/assets/jsapi/presentation_api.js', 
```
touch or change `experimental/presentation/presentation_api.js` will cause the xwalk_runtime_lib_apk target rebuild.

So it can be removed.