↓のをブックマークのURLを入れるところにコピペする。
javascript:(function(n%2Ce%2Ca%2Cc)%7Bv%3Dn%5Bn.length-1%5D%3Be.width%3Dv.videoWidth%3Be.height%3Dv.videoHeight%3Bc%3De.getContext('2d')%3Bc.drawImage(v%2C0%2C0)%3Be.toBlob(function(b)%7Ba.href%3DURL.createObjectURL(b)%3Ba.download%3DDate.now()%2B'.png'%3Ba.click()%7D%2C'image%2Fpng')%7D)(document.getElementsByTagName('video')%2Cdocument.createElement('canvas')%2Cdocument.createElement('a'))