Fix warning as error, check struct size.

ppapi/native_client/src/shared/ppapi_proxy/browser_ppb_host_resolver_private_rpc_server.cc

Index: ppapi/native_client/src/shared/ppapi_proxy/browser_ppb_host_resolver_private_rpc_server.cc
===================================================================
--- ppapi/native_client/src/shared/ppapi_proxy/browser_ppb_host_resolver_private_rpc_server.cc	(revision 128518)
+++ ppapi/native_client/src/shared/ppapi_proxy/browser_ppb_host_resolver_private_rpc_server.cc	(working copy)
@@ -159,8 +159,12 @@
     nacl_abi_size_t* addr_bytes, char* addr,
     int32_t* success) {
   NaClSrpcClosureRunner runner(done);
-  rpc->result = NACL_SRPC_RESULT_OK;
+  rpc->result = NACL_SRPC_RESULT_APP_ERROR;
 
+  if (*addr_bytes !=
+      static_cast<nacl_abi_size_t>(sizeof(PP_NetAddress_Private)))
+    return;
+
   PP_Bool pp_success =
       PPBHostResolverPrivateInterface()->GetNetAddress(
           host_resolver,
@@ -170,4 +174,6 @@
 
   DebugPrintf("PPB_HostResolver_Private::GetNetAddress: " \
               "success=%d\n", *success);
+
+  rpc->result = NACL_SRPC_RESULT_OK;
 }