Removing extensions::FeatureSwitch which is no longer used

Removing extensions::FeatureSwitch which is no longer used

BUG=357228

[krish, 2014-10-13 07:09:30]

krish.botta@samsung.com changed reviewers:
+ finnur@chromium.org

[krish, 2014-10-13 07:09:32]

PTAL

[Finnur, 2014-10-13 11:55:26]

I'm sorry, but this patch does not meet my quality standards.

In one case a bug has been introduced by hooking an else clause up to the wrong
if clause (extension_context_menu_model.cc) and it seems lines have in some
cases been deleted partially (extension_browsertest.h).

There are also numerous style issues. For example:
Indentation is never fixed when if tests are deleted nor empty lines removed
(after lines deleted).

I would also expect FeatureSwitch.h/.cc to be removed if the intent is to remove
the flags. Only then can we know if we've caught all lines that need to be
deleted.

But regardless of all this I question the timing of this patch because some of
those flags are under active development (e.g. extension_action_redesign) and
cannot be removed yet.