First leg of three-legged CacheStorage::Match implementation
First leg of three-legged CacheStorage::Match implementation

This callback type is needed by the upcoming CacheStorage::Match implementation.

Upstream of: https://codereview.chromium.org/777543003

BUG=438218

Review URL: https://codereview.chromium.org/776283002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@186691 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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