Do not close network controller in ProfileExtender if it was not opened there.
Do not close network controller in ProfileExtender if it was not opened there.

If we have a benchmark that requires running a profile extender (for example,
it has a BlankPageWithExtensionProfile page), the network_controller will be
closed when the profile extender calls TearDownBrowser(). And when later
this benchmark starts running stories, it will attempt to call StartReplay
method of network_controller, which will fail, because the network_controller
is already closed.
This CL fixes this behaviour by not closing network_controller inside the
profile extender if it was not opened in that profile extender.

The review https://codereview.chromium.org/1822083003/ adds is_open property
to NetworkController class. After it lands, I'll update this CL so that it
no longer requires protected member access.

BUG=597923

Review URL: https://codereview.chromium.org/1822043004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#383487}

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