Revert of Remove a bunch of NPAPI quirks and related support code

content/child/npapi/plugin_instance.h

Index: content/child/npapi/plugin_instance.h
diff --git a/content/child/npapi/plugin_instance.h b/content/child/npapi/plugin_instance.h
index 8eeaa3ecb8f324a95ee248dd7aa924ffef14f43e..75a1e997878f3fdaefbecf8b9ab69bfe4aa3b2da 100644
--- a/content/child/npapi/plugin_instance.h
+++ b/content/child/npapi/plugin_instance.h
@@ -75,6 +75,12 @@
 
   // NPAPI's instance identifier for this instance
   NPP npp() { return npp_; }
+
+  // Get/Set for the instance's window handle.
+  gfx::PluginWindowHandle window_handle() const { return window_handle_; }
+  void set_window_handle(gfx::PluginWindowHandle value) {
+    window_handle_ = value;
+  }
 
   // Get/Set whether this instance is transparent. This only applies to
   // windowless plugins.  Transparent plugins require that webkit paint the
@@ -221,6 +227,7 @@
   NPP                                      npp_;
   scoped_refptr<PluginHost>                host_;
   NPPluginFuncs*                           npp_functions_;
+  gfx::PluginWindowHandle                  window_handle_;
   bool                                     transparent_;
   WebPlugin*                               webplugin_;
   std::string                              mime_type_;