Pickle: handle invalid data on 64 bit systems.

      There was a problem with pointer arithmetic for 64 bit systems
so invalid data was not properly detected. Now we do explicit tests.

BUG=56449
TEST=base_unittests

Review URL: http://codereview.chromium.org/4716006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@66149 0039d316-1c4b-4281-b951-d872f2087c98