Bug 1685413 - [devtools] Re-enable devtools/client/dom/test/browser_dom_fission_target_switching.js test for Fission. r=ladybenko.

The test used to fail after navigating because the expected property
wasn't displayed.
Here we're trying to work around that by:
- using the navigateTo helper function, which takes care of waiting for the right events
- awaiting until the property is displayed (since it wasn't before), just in case the
rendering takes more time than expected.

Differential Revision: https://phabricator.services.mozilla.com/D101783

devtools/client/dom/test/browser.ini

@@ -12,7 +12,6 @@ support-files =
 [browser_dom_array.js]
 [browser_dom_basic.js]
 [browser_dom_fission_target_switching.js]
-skip-if = fission # Disable frequent fission intermittents Bug 1675020
 [browser_dom_nodes_highlight.js]
 [browser_dom_nodes_select.js]
 [browser_dom_refresh.js]

devtools/client/dom/test/browser_dom_fission_target_switching.js

@@ -15,33 +15,24 @@ add_task(async function() {
   info("Open a page that runs in the parent process");
   const { panel } = await addTestTab(PARENT_PROCESS_URI);
 
-  let _aProperty = getRowByLabel(panel, "_a");
+  const _aProperty = getRowByLabel(panel, "_a");
   let buttonProperty = getRowByLabel(panel, "button");
 
   ok(!_aProperty, "There is no _a property on the about:robots page");
   ok(buttonProperty, "There is, however, a button property on this page");
 
   info("Navigate to a page that runs in the content process");
-
-  const toolbox = panel.getToolbox();
-
   // Wait for the DOM panel to refresh.
   const onPropertiesFetched = waitForDispatch(panel, "FETCH_PROPERTIES");
   // Also wait for the toolbox to switch to the new target, to avoid hanging requests when
   // the test ends.
-  const onTargetSwitched = toolbox.targetList.once("switched-target");
+  await navigateTo(CONTENT_PROCESS_URI);
+  await onPropertiesFetched;
 
-  await toolbox.target.navigateTo({ url: CONTENT_PROCESS_URI });
+  await waitFor(() => getRowByLabel(panel, "_a"));
+  ok(true, "This time, the _a property exists on this content process page");
 
-  await Promise.all([onPropertiesFetched, onTargetSwitched]);
-
-  _aProperty = getRowByLabel(panel, "_a");
   buttonProperty = getRowByLabel(panel, "button");
-
-  ok(
-    _aProperty,
-    "This time, the _a property exists on this content process page"
-  );
   ok(
     !buttonProperty,
     "There is, however, no more button property on this page"