Remove a bunch of NPAPI quirks and related support code

BUG=493212
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_site_isolation

Committed: https://crrev.com/f8396023a9e38d3ec249cdf1f730e4b79cebbc7e
Cr-Commit-Position: refs/heads/master@{#382642}

Review URL: https://codereview.chromium.org/1813143002

Cr-Commit-Position: refs/heads/master@{#382731}
36 files changed