Add a method to the ProcessSnapshot to expose a ProcessMemory object to
allow reading memory directly from the underlying process.
CQ-DEPEND=CL:1278830
BUG=crashpad:262
Change-Id: Ied2a5510a9b051c7ac8c41cdd060e8daa531086e
Reviewed-on: https://chromium-review.googlesource.com/c/1315428
Commit-Queue: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>