[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_;
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBCallbacks);