Cleanup ext.cx.source.js

Change-Id: I147cc47fe1b88b876827c5d585a65e3c7430634e
Encode URI components for the fetch URL

Change-Id: Ie593c94d395cedddfb5f3b43c39de26c0a9ca322
Prevent undefined JS error

Bug: 68291

Change-Id: I01905a653902a39a4ee4cb2941fea000899b39bc
Merge "Cleanup ext.cx.source.js"
Merge "Encode URI components for the fetch URL"
Merge "Prevent undefined JS error"