Bug 1586119: Part 3 - Enable some tests which appear to work under Fission. r=mccr8

Differential Revision: https://phabricator.services.mozilla.com/D48222

--HG--
extra : moz-landing-system : lando

docshell/test/navigation/mochitest.ini

@@ -87,9 +87,7 @@ skip-if =
   fission # Times out.
 [test_performance_navigation.html]
 [test_sessionhistory.html]
-skip-if =
-  toolkit == 'android' || # RANDOM on android
-  (fission && debug) # Intermittent timeouts
+skip-if = toolkit == 'android' # RANDOM on android
 support-files = file_bug1379762-1.html
 [test_sibling-matching-parent.html]
 skip-if = fission # Times out.

toolkit/components/remotebrowserutils/tests/browser/browser.ini

@@ -13,6 +13,5 @@ skip-if = fission
 [browser_httpResponseProcessSelection.js]
 skip-if = fission # BrowserTestUtils.browserLoaded call that spans a process switch
 [browser_httpCrossOriginOpenerPolicy.js]
-skip-if = fission
 [browser_httpToFileHistory.js]
 [browser_oopProcessSwap.js]