Rewrite std::string("") to std::string(), Linux edition.

sync/internal_api/sync_encryption_handler_impl.cc

Index: sync/internal_api/sync_encryption_handler_impl.cc
diff --git a/sync/internal_api/sync_encryption_handler_impl.cc b/sync/internal_api/sync_encryption_handler_impl.cc
index 1a645bfcdbe83842d7d64169b65c19d2b0f962a1..655feb2877a8d758a55afdc20d7c02bea7e814ec 100644
--- a/sync/internal_api/sync_encryption_handler_impl.cc
+++ b/sync/internal_api/sync_encryption_handler_impl.cc
@@ -136,7 +136,7 @@ std::string PackKeystoreBootstrapToken(
     const std::string& current_keystore_key,
     Encryptor* encryptor) {
   if (current_keystore_key.empty())
-    return "";
+    return std::string();
 
   base::ListValue keystore_key_values;
   for (size_t i = 0; i < old_keystore_keys.size(); ++i)
@@ -1112,7 +1112,7 @@ void SyncEncryptionHandlerImpl::SetCustomPassphrase(
   if (passphrase_type_ != KEYSTORE_PASSPHRASE) {
     DVLOG(1) << "Failing to set a custom passphrase because one has already "
              << "been set.";
-    FinishSetPassphrase(false, "", trans, nigori_node);
+    FinishSetPassphrase(false, std::string(), trans, nigori_node);
     return;
   }
 
@@ -1125,7 +1125,7 @@ void SyncEncryptionHandlerImpl::SetCustomPassphrase(
     // if statement above. For the sake of safety though, we check for it in
     // case a client is misbehaving.
     LOG(ERROR) << "Failing to set custom passphrase because of pending keys.";
-    FinishSetPassphrase(false, "", trans, nigori_node);
+    FinishSetPassphrase(false, std::string(), trans, nigori_node);
     return;
   }