Too Long; Didn't Read
The W3C or World Wide Web Consortium develops open standards for the Web. The Web Standards 101 document specifies the DOM event flow, defines a list of events and their execution order. There is nothing specific about focus because it really depends on browser implementations. We need to get an overview of what each part is responsible for. Chromium is a complex piece of software with the codebase around tens of millions of lines of code. Getting Around The Chrome Source Code is a lot of different logic.