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

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 c2ede10b09f8643d4c3100420a09e04ba3b6cba9..ea32e23daa60f38c7538db82c0062c8f9826e5e5 100644
--- a/ppapi/proxy/plugin_var_tracker.h
+++ b/ppapi/proxy/plugin_var_tracker.h
@@ -56,12 +56,6 @@ class PPAPI_PROXY_EXPORT PluginVarTracker : public VarTracker {
   void ReleaseHostObject(PluginDispatcher* dispatcher,
                          const PP_Var& host_object);
 
-  // Retrieves the internal reference counts for testing. Returns 0 if we
-  // know about the object but the corresponding value is 0, or -1 if the
-  // given object ID isn't in our map.
-  int GetRefCountForObject(const PP_Var& plugin_object);
-  int GetTrackedWithNoReferenceCountForObject(const PP_Var& plugin_object);
-
  private:
   // VarTracker protected overrides.
   virtual int32 AddVarInternal(Var* var, AddVarRefMode mode) OVERRIDE;