Fix overflow in history expiry code in 64 bit builds.

Fix overflow in history expiry code in 64 bit builds.

ArchiveSomeOldHistory() takes an int as last parameter, but this code would
pass numeric_limits<size_t>::max(). Found by clang building in C++11 mode:

../../chrome/browser/history/expire_history_backend.cc:330:25: error: implicit conversion from 'unsigned long' to 'int' changes value from 18446744073709551615 to -1 [-Werror,-Wconstant-conversion]
                        std::numeric_limits<size_t>::max());
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

BUG=233330
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=195056

[brettw, 2013-04-18 23:06:18]

lgtm

[Nico, 2013-04-19 03:06:37]

Committed patchset #1 manually as r195056 (presubmit successful).