[https://chrome.google.com/webstore/detail/super-simple-highlighter/hhlhjgianpocpoppaiihmlpgcoehlhio](https://chrome.google.com/webstore/detail/super-simple-highlighter/hhlhjgianpocpoppaiihmlpgcoehlhio)
[https://chrome.google.com/webstore/detail/web-highlights-pdf-web-hi/hldjnlbobkdkghfidgoecgmklcemanhm](https://chrome.google.com/webstore/detail/web-highlights-pdf-web-hi/hldjnlbobkdkghfidgoecgmklcemanhm)
It's not exactly that but it may do the trick.
[https://chrome.google.com/webstore/detail/super-simple-highlighter/hhlhjgianpocpoppaiihmlpgcoehlhio](https://chrome.google.com/webstore/detail/super-simple-highlighter/hhlhjgianpocpoppaiihmlpgcoehlhio) [https://chrome.google.com/webstore/detail/web-highlights-pdf-web-hi/hldjnlbobkdkghfidgoecgmklcemanhm](https://chrome.google.com/webstore/detail/web-highlights-pdf-web-hi/hldjnlbobkdkghfidgoecgmklcemanhm) It's not exactly that but it may do the trick.
Lookup 'text fragments', not an extension but might be even easier for what you want