diff -up firefox-89.0/dom/base/test/browser_multiple_popups.js.mochitest-wayland-workaround firefox-89.0/dom/base/test/browser_multiple_popups.js
--- firefox-89.0/dom/base/test/browser_multiple_popups.js.mochitest-wayland-workaround	2021-05-27 22:29:44.000000000 +0200
+++ firefox-89.0/dom/base/test/browser_multiple_popups.js	2021-06-01 10:02:59.648432325 +0200
@@ -265,6 +265,7 @@ add_task(async _ => {
   info("All opened from chrome.");
   await withTestPage(2, { chrome: true }, async function(browser) {
     await BrowserTestUtils.synthesizeMouseAtCenter("#openPopups", {}, browser);
+    await BrowserTestUtils.synthesizeMouseAtCenter("#openPopups", {}, browser);
   });
 });
 
diff -up firefox-89.0/dom/ipc/BrowserChild.cpp.mochitest-wayland-workaround firefox-89.0/dom/ipc/BrowserChild.cpp
--- firefox-89.0/dom/ipc/BrowserChild.cpp.mochitest-wayland-workaround	2021-05-27 22:29:44.000000000 +0200
+++ firefox-89.0/dom/ipc/BrowserChild.cpp	2021-06-01 10:02:59.649432346 +0200
@@ -457,7 +457,7 @@ nsresult BrowserChild::Init(mozIDOMWindo
   }
   mPuppetWidget->InfallibleCreate(nullptr,
                                   nullptr,  // no parents
-                                  LayoutDeviceIntRect(0, 0, 0, 0),
+                                  LayoutDeviceIntRect(0, 0, 1000, 1000),
                                   nullptr);  // HandleWidgetEvent
 
   mWebBrowser = nsWebBrowser::Create(this, mPuppetWidget, mBrowsingContext,
diff -up firefox-89.0/toolkit/components/browser/nsWebBrowser.cpp.mochitest-wayland-workaround firefox-89.0/toolkit/components/browser/nsWebBrowser.cpp
--- firefox-89.0/toolkit/components/browser/nsWebBrowser.cpp.mochitest-wayland-workaround	2021-05-27 22:29:54.000000000 +0200
+++ firefox-89.0/toolkit/components/browser/nsWebBrowser.cpp	2021-06-01 10:02:59.649432346 +0200
@@ -150,7 +150,8 @@ already_AddRefed<nsWebBrowser> nsWebBrow
   // handler that always gets called (even for subframes) for any bubbling
   // event.
 
-  nsresult rv = docShell->InitWindow(nullptr, docShellParentWidget, 0, 0, 0, 0);
+  nsresult rv =
+      docShell->InitWindow(nullptr, docShellParentWidget, 0, 0, 1000, 1000);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return nullptr;
   }
diff -up firefox-89.0/widget/gtk/nsWindow.cpp.mochitest-wayland-workaround firefox-89.0/widget/gtk/nsWindow.cpp
--- firefox-89.0/widget/gtk/nsWindow.cpp.mochitest-wayland-workaround	2021-06-01 10:02:59.644432243 +0200
+++ firefox-89.0/widget/gtk/nsWindow.cpp	2021-06-01 10:04:28.715262874 +0200
@@ -7962,6 +7973,8 @@ nsresult nsWindow::SynthesizeNativeMouse
     nsIObserver* aObserver) {
   AutoObserverNotifier notifier(aObserver, "mouseevent");
 
+  LOG(("nsWindow::SynthesizeNativeMouseEvent [%p]\n", (void*)this));
+
   if (!mGdkWindow) {
     return NS_OK;
   }
@@ -7976,6 +7989,12 @@ nsresult nsWindow::SynthesizeNativeMouse
   switch (aNativeMessage) {
     case NativeMouseMessage::ButtonDown:
     case NativeMouseMessage::ButtonUp: {
+      if (aNativeMessage == NativeMouseMessage::ButtonDown) {
+        LOG(("    NativeMouseMessage::ButtonDown()\n"));
+      } else {
+        LOG(("    NativeMouseMessage::ButtonUp()\n"));
+      }
+
       GdkEvent event;
       memset(&event, 0, sizeof(GdkEvent));
       event.type = aNativeMessage == NativeMouseMessage::ButtonDown