Quota: Add missing return statement.

QuotaManagerProxy post tasks to call itself on the right thread, but needs
to return after posting the task and before calling anything on QuotaManager.

Bug: 997258
Change-Id: Ia6914224006e128758b62c1aed96d3d3636e9790
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2084716Reviewed-by: Joshua Bell <jsbell@chromium.org>
Commit-Queue: Jarryd Goodman <jarrydg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746491}

storage/browser/quota/quota_manager_proxy.cc

@@ -106,6 +106,7 @@ void QuotaManagerProxy::NotifyWriteFailed(const url::Origin& origin) {
     io_thread_->PostTask(
         FROM_HERE,
         base::BindOnce(&QuotaManagerProxy::NotifyWriteFailed, this, origin));
+    return;
   }
   if (manager_)
     manager_->NotifyWriteFailed(origin);