chromeos: Avoid EasyUnlockGetKeysOperation D-Bus log spam.

Make EasyUnlockGetKeysOperation wait for the cryptohome
D-Bus service to be available before making a GetKeyDataEx
method call to it. Otherwise, we get repeated log spam at
boot:

  [1912:1912:0916/102203:ERROR:object_proxy.cc(583)] Failed to call method: org.chromium.CryptohomeInterface.GetKeyDataEx: object_path= /org/chromium/Cryptohome: org.freedesktop.DBus.Error.ServiceUnknown: The name org.chromium.Cryptohome was not provided by any .service files
  [1912:1912:0916/102203:ERROR:easy_unlock_get_keys_operation.cc(61)] Easy unlock failed to get key data, code=1

BUG=636554

Review-Url: https://codereview.chromium.org/2343213002
Cr-Commit-Position: refs/heads/master@{#419228}

chrome/browser/chromeos/login/easy_unlock/easy_unlock_get_keys_operation.cc

@@ -11,6 +11,8 @@
 #include "base/bind.h"
 #include "base/logging.h"
 #include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_key_manager.h"
+#include "chromeos/dbus/cryptohome_client.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
 #include "components/proximity_auth/logging/logging.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "google_apis/gaia/gaia_auth_util.h"
@@ -30,6 +32,20 @@ EasyUnlockGetKeysOperation::~EasyUnlockGetKeysOperation() {
 }
 
 void EasyUnlockGetKeysOperation::Start() {
+  // Register for asynchronous notification of cryptohome being ready.
+  DBusThreadManager::Get()->GetCryptohomeClient()->WaitForServiceToBeAvailable(
+      base::Bind(&EasyUnlockGetKeysOperation::OnCryptohomeAvailable,
+                 weak_ptr_factory_.GetWeakPtr()));
+}
+
+void EasyUnlockGetKeysOperation::OnCryptohomeAvailable(bool available) {
+  if (!available) {
+    PA_LOG(ERROR) << "Failed to wait for cryptohome to become available";
+    callback_.Run(false, EasyUnlockDeviceKeyDataList());
+    return;
+  }
+
+  // Start the asynchronous key fetch.
   // TODO(xiyuan): Use ListKeyEx.
   key_index_ = 0;
   GetKeyData();
@@ -42,7 +58,6 @@ void EasyUnlockGetKeysOperation::GetKeyData() {
       EasyUnlockKeyManager::GetKeyLabel(key_index_),
       base::Bind(&EasyUnlockGetKeysOperation::OnGetKeyData,
                  weak_ptr_factory_.GetWeakPtr()));
-
 }
 
 void EasyUnlockGetKeysOperation::OnGetKeyData(

chrome/browser/chromeos/login/easy_unlock/easy_unlock_get_keys_operation.h

@@ -26,10 +26,19 @@ class EasyUnlockGetKeysOperation {
                              const GetKeysCallback& callback);
   ~EasyUnlockGetKeysOperation();
 
+  // Starts the operation. If the cryptohome service is not yet available, the
+  // request will be deferred until it is ready.
   void Start();
 
  private:
+  // Called once when the cryptohome service is available.
+  void OnCryptohomeAvailable(bool available);
+
+  // Asynchronously requests data for |key_index_| from cryptohome.
   void GetKeyData();
+
+  // Callback for GetKeyData(). Updates |devices_|, increments |key_index_|, and
+  // calls GetKeyData() again.
   void OnGetKeyData(
       bool success,
       cryptohome::MountError return_code,