Instant: Fix a crash where the tab is closing and Instant 'hides' the

content/browser/renderer_host/render_widget_host_view_win.cc

Index: content/browser/renderer_host/render_widget_host_view_win.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_win.cc b/content/browser/renderer_host/render_widget_host_view_win.cc
index 21bae6ca6d487098015c1e9d2234781ac7989818..340daad43e74323a04a0f683017fb29b48c9b927 100644
--- a/content/browser/renderer_host/render_widget_host_view_win.cc
+++ b/content/browser/renderer_host/render_widget_host_view_win.cc
@@ -347,7 +347,8 @@ void RenderWidgetHostViewWin::WasHidden() {
 
   // If we have a renderer, then inform it that we are being hidden so it can
   // reduce its resource utilization.
-  render_widget_host_->WasHidden();
+  if (render_widget_host_)
+    render_widget_host_->WasHidden();
 }
 
 void RenderWidgetHostViewWin::SetSize(const gfx::Size& size) {