Skip screen update when the WebView isn't ready to paint.

chrome/renderer/render_widget.cc

Index: chrome/renderer/render_widget.cc
diff --git a/chrome/renderer/render_widget.cc b/chrome/renderer/render_widget.cc
index 3252097db10ae00b63ee39809fd52ba61abac78c..28385f5fd669d897c2465d92a9b3e6ac09581382 100644
--- a/chrome/renderer/render_widget.cc
+++ b/chrome/renderer/render_widget.cc
@@ -588,6 +588,14 @@ void RenderWidget::didInvalidateRect(const WebRect& rect) {
     }
   }
 
+  // Painting a not-yet-ready page would cause flicker with white blank.
+  // So InvalidateRect() and PostTask() should be skipped.
+  // Because we expect at least one update after loading the page and
+  // InvalidateRect() without PostTask() can miss it,
+  // We skip both instead of skip only PostTask().
+  if (!IsReadyToPaint())
+    return;
+
   // We only want one pending DoDeferredUpdate call at any time...
   bool update_pending = paint_aggregator_.HasPendingUpdate();