Adding ThreadChecker validation to d'tors for host classes

remoting/host/linux/certificate_watcher.cc

Index: remoting/host/linux/certificate_watcher.cc
diff --git a/remoting/host/linux/certificate_watcher.cc b/remoting/host/linux/certificate_watcher.cc
index 1f5c66113978844139f2dfc63fadcaa4930d090b..c47c4629e61f99b86ee0ca23c3d812a9f8519dc0 100644
--- a/remoting/host/linux/certificate_watcher.cc
+++ b/remoting/host/linux/certificate_watcher.cc
@@ -98,7 +98,9 @@ CertDbContentWatcher::CertDbContentWatcher(
   thread_checker_.DetachFromThread();
 }
 
-CertDbContentWatcher::~CertDbContentWatcher() {}
+CertDbContentWatcher::~CertDbContentWatcher() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
 
 void CertDbContentWatcher::StartWatching() {
   DCHECK(!cert_watch_path_.empty());