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

ppapi/proxy/host_var_serialization_rules.h

Index: ppapi/proxy/host_var_serialization_rules.h
diff --git a/ppapi/proxy/host_var_serialization_rules.h b/ppapi/proxy/host_var_serialization_rules.h
index 9c4db2e89dcb50237116db0069f75735ba6a20e0..bbbb3d778e5852e4408572ffeb72f7d6b24677c1 100644
--- a/ppapi/proxy/host_var_serialization_rules.h
+++ b/ppapi/proxy/host_var_serialization_rules.h
@@ -18,8 +18,7 @@ namespace proxy {
 // Implementation of the VarSerializationRules interface for the host side.
 class HostVarSerializationRules : public VarSerializationRules {
  public:
-  HostVarSerializationRules(const PPB_Var* var_interface,
-                            PP_Module pp_module);
+  HostVarSerializationRules(PP_Module pp_module);
   ~HostVarSerializationRules();
 
   // VarSerialization implementation.
@@ -40,7 +39,6 @@ class HostVarSerializationRules : public VarSerializationRules {
   // string object.
   void VarToString(const PP_Var& var, std::string* str);
 
-  const PPB_Var* var_interface_;
   PP_Module pp_module_;
 
   DISALLOW_COPY_AND_ASSIGN(HostVarSerializationRules);