Carry the client ID from the database all the way through upload

Carry the client ID from the database all the way through upload.

The client ID is added to a new field, MinidumpCrashpadInfo::client_id,
in each minidump file that is written. The ProcessSnapshot::ClientID()
gives access to value at the snapshot level. In the upload thread,
client IDs are retrieved from minidump files and used to populate the
“guid” HTTP form parameter.

The Breakpad client supplies these values at upload without hyphens and
with all capital letters. Currently, the Crashpad client uses hyphens
and lowercase letters when communicating with a Breakpad server.

TEST=crashpad_minidump_test MinidumpCrashpadInfoWriter.*,
     crashpad_snapshot_test ProcessSnapshotMinidump.*,
     run_with_crashpad --handler crashpad_handler \
         -a --database=/tmp/crashpad_db \
         -a --url=https://clients2.google.com/cr/staging_report \
         -a --annotation=prod=crashpad \
         -a --annotation=ver=0.7.0 \
         crashy_program

R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/359bdd86225c144f6b24a365260b85dc617be308

[Mark Mentovai, 2015-03-11 19:39:42]

mark@chromium.org changed reviewers:
+ rsesek@chromium.org

[Mark Mentovai, 2015-03-11 19:39:42]

go/crash-staging/7fd740fc2cbe8cf7
go/crash-staging/7fd740fc2cbe8994

[Robert Sesek, 2015-03-11 20:23:17]

LGTM

[Mark Mentovai, 2015-03-11 21:10:54]

Committed patchset #1 (id:1) manually as
359bdd86225c144f6b24a365260b85dc617be308 (presubmit successful).