Pepper: Fix reentrancy problem in PepperPluginInstanceImpl.

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 d9f9d58eeb43b8617b7655b2a0248cc1c77a2852..07930b338c15720c76229694adc1951989295c0c 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.cc
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.cc
@@ -3135,6 +3135,9 @@ bool PepperPluginInstanceImpl::FlashSetFullscreen(bool fullscreen,
 }
 
 bool PepperPluginInstanceImpl::IsRectTopmost(const gfx::Rect& rect) {
+  if (is_deleted_)
+    return false;
+
   if (flash_fullscreen_)
     return true;