Before this commit, there was an issue with input method using composition in which typed characters were duplicated. This was occuring until the composition ended. This is a bug specific to Google Chrome v53+. It has been fixed in the most recent version of ace.js [1], and we just port the fix into our custom code. Note that we do not simply import ace.js as a whole, because we must update lots of custom code at the same time. We plan to do so in the future. Fixes #23629 [1] https://github.com/ajaxorg/ace/pull/3116