Bug 1619953 - P9 - Test `browser_ContentSearch.js` disabled for linux64debug when fission not enabled r=baku

This is done because the test always suffers from shutdown leaks after the changes in Bug 1619953, which make the stream acquired during the test asynchronous.

Differential Revision: https://phabricator.services.mozilla.com/D81861

browser/modules/test/browser/browser.ini

@@ -15,6 +15,7 @@ support-files =
   !/browser/components/search/test/browser/testEngine.xml
   !/browser/components/search/test/browser/testEngine_diacritics.xml
   testEngine_chromeicon.xml
+skip-if = (debug && os == "linux" && bits == 64 && os_version == "18.04" && !fission) # Bug 1649755 
 [browser_EveryWindow.js]
 [browser_LiveBookmarkMigrator.js]
 [browser_PageActions.js]