Move more code from headers to implementation.

ppapi/proxy/plugin_var_tracker.h

Index: ppapi/proxy/plugin_var_tracker.h
diff --git a/ppapi/proxy/plugin_var_tracker.h b/ppapi/proxy/plugin_var_tracker.h
index 1ae5b2407df40f8008ba622dcee5e8c3b2823312..999f2092e2fbdff743828a80f3c8e926ddee8b7c 100644
--- a/ppapi/proxy/plugin_var_tracker.h
+++ b/ppapi/proxy/plugin_var_tracker.h
@@ -30,6 +30,8 @@ class PluginVarTracker {
   // which is probably just being created from our constructor.
   PluginVarTracker(PluginDispatcher* dispatcher);
 
+  ~PluginVarTracker();
+
   // Must be called after construction.
   void Init();