Replace c/b/nss_context by a KeyedService.

chromeos/tpm_token_loader.cc

Index: chromeos/tpm_token_loader.cc
diff --git a/chromeos/tpm_token_loader.cc b/chromeos/tpm_token_loader.cc
index 856df5f251311e43afb9803f7e81397a498f1b65..fc6976657faf7400210b6313448d029b5d70298f 100644
--- a/chromeos/tpm_token_loader.cc
+++ b/chromeos/tpm_token_loader.cc
@@ -50,6 +50,8 @@ static TPMTokenLoader* g_tpm_token_loader = NULL;
 
 // static
 void TPMTokenLoader::Initialize() {
+  if (g_tpm_token_loader && g_tpm_token_loader->initialized_for_test_)
+    return;
   CHECK(!g_tpm_token_loader);
   g_tpm_token_loader = new TPMTokenLoader(false /*for_test*/);
 }