Fix a couple of integer issues in Pickle deserialization

Fix a couple of integer issues in Pickle deserialization. Neither represent
a significant risk because the code is not directly exposed to user input. In
addition, neither error leads to memory corruption. At worse, there's a C++
exception or abort().

BUG=NONE
TEST=PickleTest.EvilLengths


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=19249

[cpu_(ooo_6.6-7.5), 2009-06-25 00:33:24]

LGTM, one comment:

http://codereview.chromium.org/146121/diff/1/3
File base/pickle_unittest.cc (right):

http://codereview.chromium.org/146121/diff/1/3#newcode226
Line 226: for (int i = 0; i < 100000; ++i)
use std::string str(10000, 'A');