[IndexedDB] Mojo testing harness.

content/browser/indexed_db/indexed_db_callbacks.h

Index: content/browser/indexed_db/indexed_db_callbacks.h
diff --git a/content/browser/indexed_db/indexed_db_callbacks.h b/content/browser/indexed_db/indexed_db_callbacks.h
index 45d9e0d25f8e5e341a8ec9c09999755c93862a8a..25d19e4b25660ef023c73152962892dcd69f5124 100644
--- a/content/browser/indexed_db/indexed_db_callbacks.h
+++ b/content/browser/indexed_db/indexed_db_callbacks.h
@@ -127,7 +127,26 @@ class CONTENT_EXPORT IndexedDBCallbacks
   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);