Sanity check frame pointer while stackwalking

BUG=

Change-Id: Ib9b0fd5ba7f829f8be8cf856ab371c6540279ee5
Reviewed-on: https://chromium-review.googlesource.com/458526
Reviewed-by: Ivan Penkov <ivanpe@chromium.org>
Cr-Mirrored-From: https://chromium.googlesource.com/breakpad/breakpad
Cr-Mirrored-Commit: 6cfdde4b91447633275f6c7a169de1bbac0ba1a0
2 files changed