Chrome started hitting some crashes in v8 jitted code which happens to be
non ABI compliant and debuggers (including WinDBG) are unable to produce
meaningful stack traces.

The Breakpad stack walker has some builtin heuristics to deal with such cases.
More specifically, when unable to find a good parent frame, it scans the raw
stack to find a suitable parent frame.  The max scan size was set at 30
pointers which was (apparently) not enough to recover in this case.

I'm increasing it to 40 pointers.  I confirmed that at 34 pointers it was able
to recover however I'm setting it to 40 in order to it some slack.

I needed to update two unittests which were expecting the previous scan limit.

BUG=
R=mark@chromium.org

Review URL: https://codereview.chromium.org/1379433005 .