Eliminate CHECK from CryptohomeLibrary::LoadSystemSalt

chrome/browser/extensions/api/music_manager_private/device_id_chromeos.cc

Index: chrome/browser/extensions/api/music_manager_private/device_id_chromeos.cc
diff --git a/chrome/browser/extensions/api/music_manager_private/device_id_chromeos.cc b/chrome/browser/extensions/api/music_manager_private/device_id_chromeos.cc
index e1e0dac3d4934847371a208afe7324f822ab0fc6..0dbbf6eda2e3abc1d15c0ddcef7cb8a09bd5b02c 100644
--- a/chrome/browser/extensions/api/music_manager_private/device_id_chromeos.cc
+++ b/chrome/browser/extensions/api/music_manager_private/device_id_chromeos.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/extensions/api/music_manager_private/device_id.h"
 
+#include "base/message_loop/message_loop.h"
 #include "chromeos/cryptohome/cryptohome_library.h"
 
 namespace extensions {
@@ -14,6 +15,15 @@ namespace api {
 void DeviceId::GetMachineId(const IdCallback& callback) {
   chromeos::CryptohomeLibrary* c_home = chromeos::CryptohomeLibrary::Get();
   std::string result = c_home->GetSystemSalt();
+  if (result.empty()) {
+    // cryptohome must not be running; re-request after a delay.
+    const int64 kRequestSystemSaltDelayMs = 500;
+    base::MessageLoop::current()->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(&DeviceId::GetMachineId, callback),
+        base::TimeDelta::FromMilliseconds(kRequestSystemSaltDelayMs));
+    return;
+  }
   callback.Run(result);
 }