[OTS] Fix assertion failure on Windows debug build

* In Windows debug build, vector::operator[] does boundary check and &vec[vec.size()] causes assertion failure.
* Make sure FILEStream::Seek returns false on error.

R=yusukes@chromium.org

Review URL: https://codereview.chromium.org/16310007

git-svn-id: http://ots.googlecode.com/svn/trunk@102 a4e77c2c-9104-11de-800e-5b313e0d2bf3
2 files changed