Bug 1682030 - Remove NPAPI from dom/plugins tests. r=jmathies

Removes NPAPI plugin tests in dom/plugins, as well as the TestPlugin, as part of removing all of NPAPI plugin support.  A small handful of tests that are still relevant remain in that directory.

Differential Revision: https://phabricator.services.mozilla.com/D107138

dom/plugins/test/crashtests/crashtests.list

@@ -1,14 +1,5 @@
 HTTP load 41276-1.html
 HTTP load 48856-1.html
 HTTP load 110650-1.html
-skip-if(!haveTestPlugin) HTTP script 539897-1.html
-asserts-if(winWidget&&browserIsRemote,0-1) skip-if(!haveTestPlugin) HTTP script 540114-1.html
-skip-if(!haveTestPlugin) HTTP load 570884.html
-# This test relies on the reading of screenX/Y forcing a round trip to
-# the X server, which is a bad assumption for <browser remote>.
-# Plugin arch is going to change anyway with OOP content so skipping
-# this test for now is OK.
-skip-if(!haveTestPlugin||http.platform!="X11") HTTP load 598862.html
-skip-if(!haveTestPlugin) HTTP load 626602-1.html
 HTTP load 752340.html
 HTTP load 843086.xhtml

dom/plugins/test/mochitest/.eslintrc.js

@@ -1,9 +1,5 @@
 "use strict";
 
 module.exports = {
-  extends: [
-    "plugin:mozilla/browser-test",
-    "plugin:mozilla/chrome-test",
-    "plugin:mozilla/mochitest-test",
-  ],
+  extends: ["plugin:mozilla/browser-test", "plugin:mozilla/mochitest-test"],
 };

dom/plugins/test/mochitest/browser.ini

@@ -1,17 +1,5 @@
 [DEFAULT]
-prefs =
-  plugin.load_flash_only=false
 support-files =
   block_all_plugins.html
-  head.js
-  plugin_test.html
-  plugin_subframe_test.html
-  plugin_no_scroll_div.html
 
 [browser_blockallplugins.js]
-[browser_bug1163570.js]
-skip-if = true # Bug 1249878
-[browser_tabswitchbetweenplugins.js]
-skip-if = true #Bug 1538425
-[browser_pluginscroll.js]
-skip-if = (true || !e10s || os != "win") # Bug 1213631