Bug 1527029 - Split about:blank test from browser_ext_tabs_executeScript.js r=zombie

The browser_ext_tabs_executeScript.js test occasionally times out.
Apparently the part of the test that opens "about:blank" and awaits the
result sometimes times out (`tabs.executeScript` does not resolve).

To avoid collateral damage by this small part of the test, the
"about:blank" test has been moved to its own file.

Differential Revision: https://phabricator.services.mozilla.com/D45955

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

browser/components/extensions/test/browser/browser.ini

@@ -226,7 +226,7 @@ fail-if = fission
 skip-if = true # Bug 1521363
 [browser_ext_tabs_events_order.js]
 [browser_ext_tabs_executeScript.js]
-skip-if = (verify && !debug && (os == 'mac'))
+[browser_ext_tabs_executeScript_about_blank.js]
 [browser_ext_tabs_executeScript_good.js]
 [browser_ext_tabs_executeScript_bad.js]
 [browser_ext_tabs_executeScript_multiple.js]

browser/components/extensions/test/browser/browser_ext_tabs_executeScript.js

@@ -383,19 +383,6 @@ add_task(async function testExecuteScript() {
           await browser.tabs.remove(tab.id);
         }),
 
-        browser.tabs.create({ url: "about:blank" }).then(async tab => {
-          const result = await browser.tabs.executeScript(tab.id, {
-            code: "location.href",
-            matchAboutBlank: true,
-          });
-          browser.test.assertEq(
-            "about:blank",
-            result[0],
-            "Script executed correctly in new tab"
-          );
-          await browser.tabs.remove(tab.id);
-        }),
-
         new Promise(resolve => {
           browser.runtime.onMessage.addListener(message => {
             browser.test.assertEq(

browser/components/extensions/test/browser/browser_ext_tabs_executeScript_about_blank.js

@@ -0,0 +1,30 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function testExecuteScript_at_about_blank() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      try {
+        const tab = await browser.tabs.create({ url: "about:blank" });
+        const result = await browser.tabs.executeScript(tab.id, {
+          code: "location.href",
+          matchAboutBlank: true,
+        });
+        browser.test.assertEq(
+          "about:blank",
+          result[0],
+          "Script executed correctly in new tab"
+        );
+        await browser.tabs.remove(tab.id);
+        browser.test.notifyPass("executeScript");
+      } catch (e) {
+        browser.test.fail(`Error: ${e} :: ${e.stack}`);
+        browser.test.notifyFail("executeScript");
+      }
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish("executeScript");
+  await extension.unload();
+});