Verify promise type before casting.

media/base/cdm_promise.cc

Index: media/base/cdm_promise.cc
diff --git a/media/base/cdm_promise.cc b/media/base/cdm_promise.cc
index 13ee760ad6caff189c8b38e50d5d74d3babe1c1c..4e4040c22cd439dabbcc88e7c1b6ca938098f473 100644
--- a/media/base/cdm_promise.cc
+++ b/media/base/cdm_promise.cc
@@ -133,6 +133,23 @@ void CdmPromiseTemplate<void>::resolve() {
   resolve_cb_.Run();
 }
 
+CdmPromise::ResolveParameterType
+CdmPromiseTemplate<void>::GetResolveParameterType() const {
+  return VOID_TYPE;
+}
+
+template <>
+CdmPromise::ResolveParameterType
+CdmPromiseTemplate<std::string>::GetResolveParameterType() const {
+  return STRING_TYPE;
+}
+
+template <>
+CdmPromise::ResolveParameterType
+CdmPromiseTemplate<KeyIdsVector>::GetResolveParameterType() const {
+  return KEY_IDS_VECTOR_TYPE;
+}
+
 // Explicit template instantiation for the Promises needed.
 template class MEDIA_EXPORT CdmPromiseTemplate<std::string>;
 template class MEDIA_EXPORT CdmPromiseTemplate<KeyIdsVector>;