Bug 1581868 - Black page sometimes when restoring geckoview_example/fenix with webrender enabled. r=jnicol

Differential Revision: https://phabricator.services.mozilla.com/D55338

layout/base/PresShell.cpp

@@ -10452,6 +10452,19 @@ nsresult PresShell::SetIsActive(bool aIsActive) {
       presContext->UpdateDynamicToolbarOffset(0);
     }
   }
+
+  // When the PresShell is being reactivated, make sure that we repaint
+  // This is needed for pages living in the parent process (like about:support).
+  // Content pages are refreshed by the BrowserHost, which does not exist
+  // in parent process pages
+  if (aIsActive) {
+    if (nsIFrame* root = GetRootFrame()) {
+      FrameLayerBuilder::InvalidateAllLayersForFrame(
+          nsLayoutUtils::GetDisplayRootFrame(root));
+      root->SchedulePaint();
+    }
+  }
+
 #endif
 
   return rv;