Bug 1567760 - Fix OOM failures in browser_webconsole_inspect_cross_domain_object.js. r=nchevobbe

Differential Revision: https://phabricator.services.mozilla.com/D38985

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

devtools/client/webconsole/test/mochitest/browser_webconsole_inspect_cross_domain_object.js

@@ -16,6 +16,11 @@ const TEST_URI =
 add_task(async function() {
   requestLongerTimeout(2);
 
+  // Bug 1518138: GC heuristics are broken for this test, so that the test
+  // ends up running out of memory. Try to work-around the problem by GCing
+  // before the test begins.
+  Cu.forceShrinkingGC();
+
   const hud = await openNewTabAndConsole(
     "data:text/html;charset=utf8,<p>hello"
   );