Quick fix for memory race inherent to all subclasses of base::Thread.

This is a local fix because TSAN is complaining only about this
particular case.  A follow-up change (which will likely take more
time) will make sure this is OK across the code-base.

BUG=98716,102134


Review URL: http://codereview.chromium.org/8343062

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107755 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/browser_thread_impl.cc

@@ -43,6 +43,12 @@ 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();
 }
 
 // static