Make it possible to have 1 PpapiGlobals per thread. Update unit tests.

ppapi/proxy/host_dispatcher.cc

Index: ppapi/proxy/host_dispatcher.cc
diff --git a/ppapi/proxy/host_dispatcher.cc b/ppapi/proxy/host_dispatcher.cc
index 120518916c0f1776fe2738eb507655fda822c266..d74feaa10c63b64fba0b25035b5446e20b1df7be 100644
--- a/ppapi/proxy/host_dispatcher.cc
+++ b/ppapi/proxy/host_dispatcher.cc
@@ -71,9 +71,7 @@ HostDispatcher::HostDispatcher(base::ProcessHandle remote_process_handle,
     g_module_to_dispatcher = new ModuleToDispatcherMap;
   (*g_module_to_dispatcher)[pp_module_] = this;
 
-  const PPB_Var* var_interface =
-      static_cast<const PPB_Var*>(local_get_interface(PPB_VAR_INTERFACE));
-  SetSerializationRules(new HostVarSerializationRules(var_interface, module));
+  SetSerializationRules(new HostVarSerializationRules(module));
 
   ppb_proxy_ = reinterpret_cast<const PPB_Proxy_Private*>(
       local_get_interface(PPB_PROXY_PRIVATE_INTERFACE));