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 70e9a7b2fab54dd75a068c72f1fcbbaca6475c64..74942595ea7a15dfddb7d125ceaff686f40efe62 100644
--- a/ppapi/proxy/host_var_serialization_rules.h
+++ b/ppapi/proxy/host_var_serialization_rules.h
@@ -11,16 +11,13 @@
 #include "ppapi/c/pp_module.h"
 #include "ppapi/proxy/var_serialization_rules.h"
 
-struct PPB_Var;
-
 namespace ppapi {
 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.
@@ -41,7 +38,6 @@ 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);