Bug 1400528 - make test_bug574663.html wait until the 'blank' attribute has actually been removed, r=mconley.

dom/events/test/test_bug574663.html

@@ -105,12 +105,20 @@ function runTest() {
     // browser to 0 using the 'blank' attribute.
     // Until the blank attribute is removed, we can't send scroll events.
     SimpleTest.waitForFocus(function() {
-      SpecialPowers.loadChromeScript(_ => {
+      let chromeScript = SpecialPowers.loadChromeScript(_ => {
         Components.utils.import("resource://gre/modules/Services.jsm");
-        Services.wm.getMostRecentWindow("navigator:browser")
-                .gBrowser.selectedBrowser.removeAttribute("blank");
+        let win = Services.wm.getMostRecentWindow("navigator:browser");
+        win.requestAnimationFrame(() => {
+          win.gBrowser.selectedBrowser.removeAttribute("blank");
+          win.requestAnimationFrame(() => {
+            sendAsyncMessage("blank-attribute-removed");
+          });
+        });
+      });
+      chromeScript.promiseOneMessage("blank-attribute-removed").then(() => {
+        chromeScript.destroy();
+        waitForPaint(win, winUtils, callback);
       });
-      waitForPaint(win, winUtils, callback);
     }, win);
   };
 

dom/events/test/window_wheel_default_action.html

@@ -52,12 +52,20 @@
 // browser to 0 using the 'blank' attribute.
 // Until the blank attribute is removed, we can't send scroll events.
 SimpleTest.waitForFocus(function() {
-  SpecialPowers.loadChromeScript(_ => {
+  let chromeScript = SpecialPowers.loadChromeScript(_ => {
     Components.utils.import("resource://gre/modules/Services.jsm");
-    Services.wm.getMostRecentWindow("navigator:browser")
-            .gBrowser.selectedBrowser.removeAttribute("blank");
+    let win = Services.wm.getMostRecentWindow("navigator:browser");
+    win.requestAnimationFrame(() => {
+      win.gBrowser.selectedBrowser.removeAttribute("blank");
+      win.requestAnimationFrame(() => {
+        sendAsyncMessage("blank-attribute-removed");
+      });
+    });
+  });
+  chromeScript.promiseOneMessage("blank-attribute-removed").then(() => {
+    chromeScript.destroy();
+    runTests();
   });
-  runTests();
 }, window);
 
 SimpleTest.requestFlakyTimeout("untriaged");