media: Avoid access violation in MojoCdm after connection error

media/base/cdm_session_tracker.cc

Index: media/base/cdm_session_tracker.cc
diff --git a/media/base/cdm_session_tracker.cc b/media/base/cdm_session_tracker.cc
index a60de0356038eaf21251cc197f6777809e60475f..b5b89908f2ed2d46aad9760312cf19708f267ec1 100644
--- a/media/base/cdm_session_tracker.cc
+++ b/media/base/cdm_session_tracker.cc
@@ -9,7 +9,7 @@ namespace media {
 CdmSessionTracker::CdmSessionTracker() {}
 
 CdmSessionTracker::~CdmSessionTracker() {
-  DCHECK(session_ids_.empty());
+  DCHECK(!HasRemainingSessions());
 }
 
 void CdmSessionTracker::AddSession(const std::string& session_id) {
@@ -32,4 +32,8 @@ void CdmSessionTracker::CloseRemainingSessions(
     session_closed_cb.Run(session_id);
 }
 
+bool CdmSessionTracker::HasRemainingSessions() const {
+  return !session_ids_.empty();
+}
+
 }  // namespace media