[Chromecast] Fix small typo in Playready codepath

This wasn't caught because it's not compiled by default.

BUG=

Review-Url: https://codereview.chromium.org/2037213003
Cr-Commit-Position: refs/heads/master@{#397879}

chromecast/renderer/key_systems_cast.cc

@@ -58,7 +58,7 @@ class PlayReadyKeySystemProperties : public ::media::KeySystemProperties {
     return EmeSessionTypeSupport::NOT_SUPPORTED;
 #else
     return persistent_license_support_ ? EmeSessionTypeSupport::SUPPORTED
-        : EmeSessionType::NOT_SUPPORTED;
+        : EmeSessionTypeSupport::NOT_SUPPORTED;
 #endif
   }