Flash is not entirely dead yet, so support can't be completely dropped. However, both Chrome [1] and Firefox [2] have announced long-term schedules for removing support for Flash, bit by bit.
As for PDF, the PDF viewers shipped in browsers seem to be much more hardened against attack than the stand alone ones people use, so as a practical matter, including a PDF viewer helps keep users safe.
As for PDF, the PDF viewers shipped in browsers seem to be much more hardened against attack than the stand alone ones people use, so as a practical matter, including a PDF viewer helps keep users safe.
[1] https://chrome.googleblog.com/2016/08/flash-and-chrome.html
[2] https://blog.mozilla.org/futurereleases/2016/07/20/reducing-...