Some device return historysize==0.
Add vp8_cx_iface.c for patch.
Overflow fix.
Update libwebm with overflow fix.
temp check-in for record purpose. Overflow fix.
Revert "temp check-in for record purpose. Overflow fix."

This reverts commit c8c5d0a8c7ec1d1cb9a5817e424f0b4a6b94ea00.
Fix degrade of pause.
Ver 2.5