Fix slow loading and render of Javascript XML import

I am working on top of open source code (code dot org) and notice that the XML import and render is extremely slow. The code it was forked from (Google blockly) is much faster. Want to fix the main performance blockers so that the code runs much faster. Can refer to the blockly code if needed to see how it is resolved in the new codebase. You can find more details on reproducing the issue here : [login to view URL] The project would be considered done when the performance of the old codebase is comparable to the new one for the [login to view URL] file attached below