Incorrect offset key position

The postion should start from 0, test case:

1. make a page with 3 topics.
2. change to load 2 topics per load
3. error will appear

See also gerrit 131911 for the cache bug in current master

Bug: 64938
Change-Id: Ic5da533279c6e58db9a9fa93ff491b4316cbd7f0
Merge "Incorrect offset key position"