For stack frame types that don't provide their own Print function, we
used to print nothing at all. Now we print at least the type and the pc.

Bug: 
Change-Id: I8453d705589bc83c284ce4eb4e981f2ad32ee901
Reviewed-on: https://chromium-review.googlesource.com/897425
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51053}