Add DCHECK to ensure IndexedDBDispatcher doesn't get re-created.

content/common/indexed_db/indexed_db_dispatcher.cc

Index: content/common/indexed_db/indexed_db_dispatcher.cc
diff --git a/content/common/indexed_db/indexed_db_dispatcher.cc b/content/common/indexed_db/indexed_db_dispatcher.cc
index b778ca2749435b088d526c2f638fe52794084979..a914f9e22ccabf9fe136d2d050fe8b0cac14a8a4 100644
--- a/content/common/indexed_db/indexed_db_dispatcher.cc
+++ b/content/common/indexed_db/indexed_db_dispatcher.cc
@@ -38,6 +38,9 @@ static base::LazyInstance<ThreadLocalPointer<IndexedDBDispatcher> >::Leaky
 
 namespace {
 
+IndexedDBDispatcher* const kHasBeenDeleted =
+    reinterpret_cast<IndexedDBDispatcher*>(0x1);
+
 int32 CurrentWorkerId() {
   return WorkerTaskRunner::Instance()->CurrentWorkerId();
 }
@@ -51,10 +54,14 @@ IndexedDBDispatcher::IndexedDBDispatcher() {
 }
 
 IndexedDBDispatcher::~IndexedDBDispatcher() {
-  g_idb_dispatcher_tls.Pointer()->Set(NULL);
+  g_idb_dispatcher_tls.Pointer()->Set(kHasBeenDeleted);
 }
 
 IndexedDBDispatcher* IndexedDBDispatcher::ThreadSpecificInstance() {
+  if (g_idb_dispatcher_tls.Pointer()->Get() == kHasBeenDeleted) {
+    NOTREACHED() << "Re-instantiating TLS IndexedDBDispatcher.";
+    g_idb_dispatcher_tls.Pointer()->Set(NULL);
+  }
   if (g_idb_dispatcher_tls.Pointer()->Get())
     return g_idb_dispatcher_tls.Pointer()->Get();