[GTK] Failed to create GBM buffer of size 0x0: Invalid argument

https://bugs.webkit.org/show_bug.cgi?id=265154

Reviewed by Michael Catanzaro.

This happens because in some cases we schedule a layer flush before the
drawing area size is initially updated. It's easier to happen in the
case of inspector because we don't delay the web process creation until
the first load in that case. We should just ignore layer flush requests
when the view size is empty since we won't be able to render anything
anyway. Also set the device scale factor before the page is initialized
to avoid sending an IPC message right after web page creation.

* Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp:
(webkitWebViewBaseCreateWebPage):
* Source/WebKit/WebProcess/WebPage/CoordinatedGraphics/LayerTreeHost.cpp:
(WebKit::LayerTreeHost::scheduleLayerFlush):

Canonical link: https://commits.webkit.org/276337@main

Source/WebKit/UIProcess/API/gtk/WebKitWebViewBase.cpp

@@ -2581,14 +2581,14 @@ void webkitWebViewBaseCreateWebPage(WebKitWebViewBase* webkitWebViewBase, Ref<AP
     }
 
     priv->pageProxy = processPool->createWebPage(*priv->pageClient, WTFMove(configuration));
+    priv->pageProxy->setIntrinsicDeviceScaleFactor(gtk_widget_get_scale_factor(GTK_WIDGET(webkitWebViewBase)));
     priv->acceleratedBackingStore = AcceleratedBackingStore::create(*priv->pageProxy);
     priv->pageProxy->initializeWebPage();
 
     if (priv->displayID)
         priv->pageProxy->windowScreenDidChange(priv->displayID);
 
     // We attach this here, because changes in scale factor are passed directly to the page proxy.
-    priv->pageProxy->setIntrinsicDeviceScaleFactor(gtk_widget_get_scale_factor(GTK_WIDGET(webkitWebViewBase)));
     g_signal_connect(webkitWebViewBase, "notify::scale-factor", G_CALLBACK(deviceScaleFactorChanged), nullptr);
 }
 

Source/WebKit/WebProcess/WebPage/CoordinatedGraphics/LayerTreeHost.cpp

@@ -129,6 +129,9 @@ void LayerTreeHost::scheduleLayerFlush()
     if (!m_layerFlushSchedulingEnabled)
         return;
 
+    if (m_webPage.size().isEmpty())
+        return;
+
     if (m_isWaitingForRenderer) {
         m_scheduledWhileWaitingForRenderer = true;
         return;