Clang's validation is a bit more thorough than GCC's or MSVC's and
picked up a few new errors and warnings. We missed a few default
cases in switches and used an improper type for default arguments.

BUG=angle:568

Change-Id: I34239c6c5c785ad1e62917fc37c3243f4c5b5f1b
Reviewed-on: https://chromium-review.googlesource.com/195472Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>