[HttpCache] added a test (cached content should be kept after purging)
merged branch bamarni/issue-6830 (PR #7408)

This PR was merged into the 2.1 branch.

Commits
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54609b9 [HttpCache] added a test (cached content should be kept after purging)

Discussion
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[HttpCache] added a test (cached content should be kept after purging)

closes #6830
Merge branch '2.1' into 2.2

* 2.1:
  Add a public modifier to an interface method
  [HttpRequest] fixes Request::getLanguages() bug
  [HttpCache] added a test (cached content should be kept after purging)
  [DoctrineBridge] Fixed non-utf-8 recognition
  [Security] fixed HttpUtils class tests