Bug 1801168, only expect the full screen exited event when the inDOMFullscreen attribute is set and select the url only in this case, r=dao

Differential Revision: https://phabricator.services.mozilla.com/D162857

browser/base/content/tabbrowser.js

@@ -1412,20 +1412,22 @@
           }
         };
 
-        if (!window.fullScreen) {
-          selectURL();
-          return;
-        }
-
-        if (newTab.isEmpty) {
-          // Wait until fullscreen has exited since it will
-          // change the selection.
+        // This inDOMFullscreen attribute indicates that the page has something
+        // such as a video in fullscreen mode. Opening a new tab will cancel
+        // fullscreen mode, so we need to wait for that to happen and then
+        // select the url field.
+        if (window.document.documentElement.hasAttribute("inDOMFullscreen")) {
           window.addEventListener("MozDOMFullscreen:Exited", selectURL, {
             once: true,
             wantsUntrusted: false,
           });
           return;
         }
+
+        if (!window.fullScreen || newTab.isEmpty) {
+          selectURL();
+          return;
+        }
       }
 
       // Focus the find bar if it was previously focused for that tab.

browser/base/content/test/tabs/browser_tabswitch_select.js

@@ -30,6 +30,34 @@ add_task(async function() {
   is(gURLBar.selectionStart, 0, "url is selected");
   is(gURLBar.selectionEnd, 22, "url is selected");
 
+  // Now check that the url bar is focused when a new tab is opened while in fullscreen.
+
+  let fullScreenEntered = TestUtils.waitForCondition(
+    () => document.documentElement.getAttribute("sizemode") == "fullscreen"
+  );
+  BrowserFullScreen();
+  await fullScreenEntered;
+
+  tab2.linkedBrowser.focus();
+
+  // Open a new tab
+  focusPromise = BrowserTestUtils.waitForEvent(
+    gURLBar.inputField,
+    "focus",
+    true
+  );
+  EventUtils.synthesizeKey("T", { accelKey: true });
+  await focusPromise;
+
+  is(document.activeElement, gURLBar.inputField, "urlbar is focused");
+
+  let fullScreenExited = TestUtils.waitForCondition(
+    () => document.documentElement.getAttribute("sizemode") != "fullscreen"
+  );
+  BrowserFullScreen();
+  await fullScreenExited;
+
+  BrowserTestUtils.removeTab(gBrowser.selectedTab);
   BrowserTestUtils.removeTab(tab1);
   BrowserTestUtils.removeTab(tab2);
 });