[IndexedDB] Fixed transaction use-after-free vuln

Bug: 725032
Change-Id: I689ded6c74d5563403587b149c3f3e02e807e4aa
Reviewed-on: https://chromium-review.googlesource.com/518483
Reviewed-by: Joshua Bell <jsbell@chromium.org>
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#475952}
void IndexedDBConnection::ActivatePendingObservers(
    std::vector<std::unique_ptr<IndexedDBObserver>> pending_observers) {
  for (auto& observer : pending_observers) {
    active_observers_.push_back(std::move(observer));
  }
  pending_observers.clear();
}

void IndexedDBConnection::ActivatePendingObservers(
    std::vector<std::unique_ptr<IndexedDBObserver>> pending_observers) {
  for (auto& observer : pending_observers) {
    active_observers_.push_back(std::move(observer));
  }
  pending_observers.clear();
}
