This fixes bug http://code.google.com/p/chromium/issues/detail?id=3881, which...

webkit/glue/webplugin_impl.cc

Index: webkit/glue/webplugin_impl.cc
===================================================================
--- webkit/glue/webplugin_impl.cc	(revision 4311)
+++ webkit/glue/webplugin_impl.cc	(working copy)
@@ -188,6 +188,26 @@
   impl_->handleEvent(event);
 }
 
+void WebPluginContainer::frameRectsChanged() const {
+  WebCore::Widget::frameRectsChanged();
+  // This is a hack to tickle re-positioning of the plugin in the case where
+  // our parent view was scrolled.
+  impl_->setFrameRect(frameRect());
+}
+
+// We override this function, to make sure that geometry updates are sent
+// over to the plugin. For e.g. when a plugin is instantiated it does
+// not have a valid parent. As a result the first geometry update from
+// webkit is ignored. This function is called when the plugin eventually
+// gets a parent.
+void WebPluginContainer::setParentVisible(bool visible) {
+  WebCore::Widget::setParentVisible(visible);
+  if (visible)
+    show();
+  else
+    hide();
+}
+
 void WebPluginContainer::windowCutoutRects(const WebCore::IntRect& bounds,
                                            WTF::Vector<WebCore::IntRect>*
                                            cutouts) const {
@@ -590,16 +610,6 @@
   }
 }
 
-void WebPluginImpl::geometryChanged() const {
-  if (!widget_)
-    return;
-
-  // This is a hack to tickle re-positioning of the plugin in the case where
-  // our parent view was scrolled.
-  const_cast<WebPluginImpl*>(this)->widget_->setFrameRect(
-      widget_->frameRect());
-}
-
 void WebPluginImpl::setFrameRect(const WebCore::IntRect& rect) {
   // Compute a new position and clip rect for ourselves relative to the
   // containing window.  We ask our delegate to reposition us accordingly.