This change removes base::Value::IsType in the //chrome directory.

It is superfluous and not part of the new API. Existing usages are
replaced by base::Value::is_* if possible (e.g. |val.is_int()| instead
of |val.IsType(base::Value::Type::INTEGER)|). Otherwise, |type()| in
combination with operator== is used (e.g. |val.type() == type| instead
of |val.IsType(type)|).

Bug: 646113
Change-Id: Id285b993173ec190fa0a68487c7be813d4952256
Reviewed-on: https://chromium-review.googlesource.com/732655


Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510829}