Fixes AppCache + ESI + Stopwatch problem
merged branch jfsimon/issue-6227 (PR #7180)

This PR was submitted for the master branch but it was merged into the 2.2 branch instead (closes #7180).

Commits
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6a33bc2 [HttpKernel] Fixes AppCache + ESI + Stopwatch problem

Discussion
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[HttpKernel] Fixes AppCache + ESI + Stopwatch problem

There is a very special case when using builtin AppCache class as kernel wrapper, in the case of an ESI request leading to a `stale` response [B]  inside a `fresh` cached response [A]. In this case, `$token` contains the [B] debug token, but the  open `stopwatch` section ID is equal to the [A] debug token. Trying to reopen section with the [B] token throws an exception which must be caught.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| Bug mask?     | no, does @vicb agree?
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6227, #6230

I tried to find a better solution than just wrapping thrown exceptions with `try/catch`, but IMHO the #6230 solution from @lsmith77 was in fine the best one. I just added some comments in the code to avoid the WTF reactions while reading it.

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by vicb at 2013-02-25T16:51:51Z

@vicb never agrees :)

I don't have time to check this deeply now but I would like to see a UT.

Could your use case be expressed as "on nested terminate events" ?

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by jfsimon at 2013-02-25T16:58:49Z

@vicb If I had an idea on how to write a conclusive test for that, I swear, it would be provided in this PR.