[microdump] Add build fingerprint and product info metadata.

[microdump] Add build fingerprint and product info metadata.

This is to add build fingerprint and product name/version to
microdumps. Conversely to what happens in the case of minidumps
with MIME fields, due to the nature of minidumps, extra metadata
cannot be reliably injected after the dump is completed.
This CL adds the plumbing to inject two optional fields plus the
corresponding tests.

BUG=chromium:410294
R=thestig@chromium.org

Committed: https://code.google.com/p/google-breakpad/source/detail?r=1456

[Primiano Tucci (use gerrit), 2015-05-14 15:23:17]

primiano@chromium.org changed reviewers:
+ thestig@chromium.org

[Primiano Tucci (use gerrit), 2015-05-14 15:23:18]

Lei, I'm sorry for the huge delay of this response, I got derailed in the next
months by other fires.
This is a follow up to https://breakpad.appspot.com/9794002/
Breakpad apparently moved here to chromium's rietveld and I cannot upload
patchset there anymore.

Patchset 1 here is == PS1 that you reviewed on the other side.
I added the response changes here in PS2.

Given that we are close to the branch point, I'd make the changes using setters
at the moment (easier to revert without multi-side dances), and refactor and
move them to the ctor in 1 month.

Thanks

[Lei Zhang, 2015-05-14 19:09:56]

lgtm

[Primiano Tucci (use gerrit), 2015-05-15 08:43:10]

Committed patchset #2 (id:20001) manually as 1456 (presubmit successful).