Bug 1527922 - Remove DevTools button in browser_toolbarKeyNav.js to prevent branch-specific focus in toolbar r=Gijs

Differential Revision: https://phabricator.services.mozilla.com/D22876

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

browser/base/content/test/keyboard/browser_toolbarKeyNav.js

@@ -11,6 +11,10 @@
 
 const PERMISSIONS_PAGE = "https://example.com/browser/browser/base/content/test/permissions/permissions.html";
 
+// The DevEdition has the DevTools button in the toolbar by default. Remove it
+// to prevent branch-specific rules what button should be focused.
+CustomizableUI.removeWidgetFromArea("developer-button");
+
 async function expectFocusAfterKey(aKey, aFocus, aAncestorOk = false) {
   let res = aKey.match(/^(Shift\+)?(?:(.)|(.+))$/);
   let shift = Boolean(res[1]);
@@ -230,3 +234,7 @@ add_task(async function testArrowsOverflowButton() {
     await expectFocusAfterKey("ArrowLeft", "sidebar-button");
   });
 });
+
+registerCleanupFunction(async function resetToolbar() {
+  await CustomizableUI.reset();
+});