Version 4.3.61.32 (cherry-pick)

Merged f6b71512

Serializer: do not miss outdated contexts if they are serialized deferred.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/1210503002.

Cr-Commit-Position: refs/branch-heads/4.3@{#37}
Cr-Branched-From: f5c0a23a-refs/heads/4.3.61@{#1}
Cr-Branched-From: 0a7d4f49-refs/heads/master@{#27508}