certificate manager: Disable export option for TPM-backed certs.

chrome/browser/certificate_manager_model.cc

Index: chrome/browser/certificate_manager_model.cc
diff --git a/chrome/browser/certificate_manager_model.cc b/chrome/browser/certificate_manager_model.cc
index 6989f723dea466d84a4757c467d724845258854a..b124a08df1b8fabec3f42ded6876664d2a521f4e 100644
--- a/chrome/browser/certificate_manager_model.cc
+++ b/chrome/browser/certificate_manager_model.cc
@@ -81,9 +81,7 @@ string16 CertificateManagerModel::GetColumnText(
 
 #if defined(OS_CHROMEOS)
       // TODO(xiyuan): Put this into a column when we have js tree-table.
-      if (crypto::IsTPMTokenReady() &&
-          cert.os_cert_handle()->slot ==
-            cert_db().GetPrivateModule()->os_module_handle()) {
+      if (IsHardwareBacked(&cert)) {
         rv = l10n_util::GetStringFUTF16(
             IDS_CERT_MANAGER_HARDWARE_BACKED_KEY_FORMAT,
             rv,
@@ -153,3 +151,14 @@ bool CertificateManagerModel::Delete(net::X509Certificate* cert) {
     Refresh();
   return result;
 }
+
+bool CertificateManagerModel::IsHardwareBacked(
+    const net::X509Certificate* cert) const {
+#if defined(OS_CHROMEOS)
+  return crypto::IsTPMTokenReady() &&
+         cert->os_cert_handle()->slot ==
+             cert_db().GetPrivateModule()->os_module_handle();
+#else
+  return false;
+#endif
+}