Thread::Stop() must be called before any subclass's destructor completes.

content/browser/browser_thread_impl.cc

Index: content/browser/browser_thread_impl.cc
diff --git a/content/browser/browser_thread_impl.cc b/content/browser/browser_thread_impl.cc
index ef5be1b0c045ce544e8cb531eb77e63322b29d6a..4b85b616cac113a76d6efae2fa73259e5f64ea60 100644
--- a/content/browser/browser_thread_impl.cc
+++ b/content/browser/browser_thread_impl.cc
@@ -43,11 +43,6 @@ BrowserThreadImpl::BrowserThreadImpl(BrowserThread::ID identifier,
 }
 
 BrowserThreadImpl::~BrowserThreadImpl() {
-  // Subclasses of base::Thread() (or at least the most-derived
-  // subclass) must call Stop() in their destructor, otherwise the
-  // vtable for the object can change while the thread's message loop
-  // is still running, and it uses the object's vtable (it calls the
-  // virtual method Run).
   Stop();
 }
 
@@ -139,6 +134,7 @@ DeprecatedBrowserThread::DeprecatedBrowserThread(BrowserThread::ID identifier,
     : BrowserThread(identifier, message_loop) {
 }
 DeprecatedBrowserThread::~DeprecatedBrowserThread() {
+  Stop();
 }
 
 // An implementation of MessageLoopProxy to be used in conjunction