[IndexedDB] Mojo testing harness.

content/browser/indexed_db/indexed_db_callbacks.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_
 #define CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 109 matching lines @@
   // OnSuccess(Connection) doesn't create an extra one.
   bool connection_created_ = false;
 
   // Used to assert that OnSuccess is only called if there was no data loss.
   blink::WebIDBDataLoss data_loss_;
 
   // The "blocked" event should be sent at most once per request.
   bool sent_blocked_ = false;
   base::TimeTicks connection_open_start_time_;
 
-  std::unique_ptr<IOThreadHelper, BrowserThread::DeleteOnIOThread> io_helper_;
+  // Required for unittests so that are scheduled on a taskrunner.
+  struct DeleteOnIOThreadTaskRunner {
+    template <typename T>
+    static void Destruct(const T* x) {
+      if (!BrowserThread::DeleteSoon(BrowserThread::IO, FROM_HERE, x)) {
+#if defined(UNIT_TEST)
+        // Only logged under unit testing because leaks at shutdown
+        // are acceptable under normal circumstances.
+        LOG(ERROR) << "DeleteSoon failed on IO thread";
+#endif  // UNIT_TEST
+      }
+    }
+    template <typename T>
+    inline void operator()(T* ptr) const {
+      enum { type_must_be_complete = sizeof(T) };
+      Destruct(ptr);
+    }
+  };
+
+  std::unique_ptr<IOThreadHelper, DeleteOnIOThreadTaskRunner> io_helper_;

[Reilly Grant (use Gerrit), 2017/05/11 01:57:08]

Why did you copy this code from BrowserThread::DeleteOnIOThread?

[dmurph, 2017/05/12 01:22:06]

Not a perfect copy - DeleteOnIOThread actually deletes the object immediately if
we're on the correct thread. Because the code relies on this around scheduling
tasks inside the class, and in the unittests I can't change the 'thread' I'm on,
I have to do this.

Let me know if you know a better way!

[Reilly Grant (use Gerrit), 2017/05/12 01:46:52]

I don't understand this last sentence. In unit tests you can still post tasks to
other threads. If you need to perform an action on the IDB thread and make sure
that tasks it posts to the IO thread happen before the run loop finishes you can
do this,

base::RunLoop loop;
db_task_runner_->PostTaskAndReply(FROM_HERE, idb_task_closure,
loop.QuitClosure());
loop.Run();

   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBCallbacks);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_