Reland: [IndexedDB] Delete callbacks state on worker thread exit.

content/child/indexed_db/indexed_db_dispatcher.h

Index: content/child/indexed_db/indexed_db_dispatcher.h
diff --git a/content/child/indexed_db/indexed_db_dispatcher.h b/content/child/indexed_db/indexed_db_dispatcher.h
index f42f4ac8990dabbd6ee9a6ae3384b0c1972f374f..d93efd67d61e861b5cceef283ef4179ebebd4352 100644
--- a/content/child/indexed_db/indexed_db_dispatcher.h
+++ b/content/child/indexed_db/indexed_db_dispatcher.h
@@ -85,6 +85,16 @@ class CONTENT_EXPORT IndexedDBDispatcher : public WorkerThread::Observer {
   FRIEND_TEST_ALL_PREFIXES(IndexedDBDispatcherTest, CursorReset);
   FRIEND_TEST_ALL_PREFIXES(IndexedDBDispatcherTest, CursorTransactionId);
 
+  // Looking up move-only entries in an std::unordered_set and removing them
+  // with out freeing them seems to be impossible so use a map instead so that
+  // the key type can remain a raw pointer.
+  using CallbackStateSet = std::unordered_map<
+      IndexedDBCallbacksImpl::InternalState*,
+      std::unique_ptr<IndexedDBCallbacksImpl::InternalState>>;
+  using DatabaseCallbackStateSet =
+      std::unordered_map<blink::WebIDBDatabaseCallbacks*,
+                         std::unique_ptr<blink::WebIDBDatabaseCallbacks>>;
+
   static int32_t CurrentWorkerId() { return WorkerThread::GetCurrentId(); }
 
   // IDBCallback message handlers.
@@ -99,10 +109,9 @@ class CONTENT_EXPORT IndexedDBDispatcher : public WorkerThread::Observer {
   // destroyed on thread exit if the Mojo pipe is not yet closed. Otherwise the
   // object will leak because the thread's task runner is no longer executing
   // tasks.
-  std::unordered_set<IndexedDBCallbacksImpl::InternalState*>
-      mojo_owned_callback_state_;
-  std::unordered_set<blink::WebIDBDatabaseCallbacks*>
-      mojo_owned_database_callback_state_;
+  CallbackStateSet mojo_owned_callback_state_;
+  DatabaseCallbackStateSet mojo_owned_database_callback_state_;
+  bool in_destructor_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBDispatcher);
 };