cryptohome: Make CryptohomeClient::Unmount non-blocking

chromeos/dbus/cryptohome_client.cc

Index: chromeos/dbus/cryptohome_client.cc
diff --git a/chromeos/dbus/cryptohome_client.cc b/chromeos/dbus/cryptohome_client.cc
index 8cfc527b6bacad6a6d736527e95634fc95db14b7..19a77281ca4581653af09ea3b738dcaf93d6a929 100644
--- a/chromeos/dbus/cryptohome_client.cc
+++ b/chromeos/dbus/cryptohome_client.cc
@@ -87,10 +87,10 @@ class CryptohomeClientImpl : public CryptohomeClient {
   }
 
   // CryptohomeClient override.
-  bool Unmount(bool* success) override {
+  void Unmount(const BoolDBusMethodCallback& callback) override {
     dbus::MethodCall method_call(cryptohome::kCryptohomeInterface,
                                  cryptohome::kCryptohomeUnmount);
-    return CallBoolMethodAndBlock(&method_call, success);
+    CallBoolMethod(&method_call, callback);
   }
 
   // CryptohomeClient override.