[Sync] Add support for performing a GetKey on startup.

sync/util/cryptographer.cc

Index: sync/util/cryptographer.cc
diff --git a/sync/util/cryptographer.cc b/sync/util/cryptographer.cc
index 59e8a1aceb0d988592459cbc35d6a3f5eae99ac6..47eb1997f5146cd07c90f4b4f02646d5574d13b2 100644
--- a/sync/util/cryptographer.cc
+++ b/sync/util/cryptographer.cc
@@ -25,6 +25,7 @@ Cryptographer::Observer::~Observer() {}
 Cryptographer::Cryptographer(Encryptor* encryptor)
     : encryptor_(encryptor),
       default_nigori_(NULL),
+      keystore_nigori_(NULL),
       encrypted_types_(SensitiveTypes()),
       encrypt_everything_(false) {
   DCHECK(encryptor);
@@ -308,6 +309,26 @@ Cryptographer::UpdateResult Cryptographer::Update(
   return Cryptographer::SUCCESS;
 }
 
+bool Cryptographer::SetKeystoreKey(const std::string& keystore_key) {
+  if (keystore_key.empty())
+    return false;
+  KeyParams params = {"localhost", "dummy", keystore_key};
+
+  // AddKey updates the default nigori, so we save the current default and
+  // make sure the keystore_nigori_ gets updated instead.
+  NigoriMap::value_type* old_default = default_nigori_;
+  if (AddKey(params)) {
+    keystore_nigori_ = default_nigori_;
+    default_nigori_ = old_default;
+    return true;
+  }
+  return false;
+}
+
+bool Cryptographer::HasKeystoreKey() {
+  return keystore_nigori_ != NULL;
+}
+
 // Static
 syncer::ModelTypeSet Cryptographer::SensitiveTypes() {
   // Both of these have their own encryption schemes, but we include them