Fix MSVC build on 64-bit

Mostly int<->size_t implicit conversions.

Warning 4366 (The result of the unary '&' operator may be unaligned)
appears in minidump.cc:907, but I don't know why. It looks aligned to me.

Change-Id: I641942adc324f8f9832b20662083dc83498688a8
Reviewed-on: https://chromium-review.googlesource.com/637390
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Cr-Mirrored-From: https://chromium.googlesource.com/breakpad/breakpad
Cr-Mirrored-Commit: 09df67311f4621cc7504e2281d90241e7605a278
7 files changed