Fix crash when a frame is detached while a PepperPluginInstance is being constructed.

content/renderer/pepper/pepper_plugin_instance_impl.cc

Index: content/renderer/pepper/pepper_plugin_instance_impl.cc
diff --git a/content/renderer/pepper/pepper_plugin_instance_impl.cc b/content/renderer/pepper/pepper_plugin_instance_impl.cc
index 0baa32e1b2796778b62d20d085e3c136dc8ffc6e..ce91ee3a1b2f9ee7a708875ebe6fdb3f39508174 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.cc
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.cc
@@ -538,8 +538,8 @@ PepperPluginInstanceImpl::PepperPluginInstanceImpl(
   memset(&current_print_settings_, 0, sizeof(current_print_settings_));
   module_->InstanceCreated(this);
 
-  if (render_frame) {  // NULL in tests
-    render_frame->PepperInstanceCreated(this);
+  if (render_frame_) {  // NULL in tests or if the frame has been destroyed.
+    render_frame_->PepperInstanceCreated(this);
     view_data_.is_page_visible = !render_frame_->GetRenderWidget()->is_hidden();
 
     // Set the initial focus.