Fixed comments around choice of C runtime.

BUG=angle:733

Change-Id: Ia1add30d54c3a7d08effca6660f98c99cb3981c2
Reviewed-on: https://chromium-review.googlesource.com/226377
Tested-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Revert "Changes gl::RenderbufferStorage to rx::RenderbufferImpl"

This reverts commit 9fc51d90176dcf4273cd6689968e1ca5d1c9fe16.

Change-Id: I4134ebe5ef6b8f509f4cc5cc22a2d526ec43ef6d
Reviewed-on: https://chromium-review.googlesource.com/226374
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Shannon Woods <shannonwoods@chromium.org>