Disable NPAPI support by removing the --enable-npapi switch, chrome://flags and enterprise policy override.

--enable-npapi-for-testing will remain temporarily until the rest of the NPAPI code and tests are removed.

This is a selective revert of 0539f2f5214fc17fdd5d1964be0ceedf98fdb9ce and 26d09db19381c2236a2890c045761465c78bc958.

BUG=493212,489066

Review URL: https://codereview.chromium.org/1158423003

Cr-Commit-Position: refs/heads/master@{#332006}
22 files changed