The next big piece of functionality in snapshot. There's a bit more
grubbing around in the NT internals than would be nice, and it has
made me start to question the value avoiding MinidumpWriteDump. But
this seems to extract most of the data we need (I haven't pulled
the cpu context yet, but I hope that won't be too hard.)
R=mark@chromium.org
BUG=crashpad:1
Review URL: https://codereview.chromium.org/1131473005
