The yoffset calculation in oc_dec_init_dummy_frame was incorrect.
The yoffset calculation in oc_dec_init_dummy_frame was incorrect.

This was only used when a stream started without a keyframe, and was
 initializing the wrong region of memory.
This was harmless (the region it initialized was still safely
 allocated, it just didn't cover all of the frame we wanted to use
 as a reference frame), but lead to unpredictable results and
 valgrind errors.
See https://bugzilla.mozilla.org/show_bug.cgi?id=625773


git-svn-id: 8dbf393e6e9ab8d4979d29f9a341a98016792aa6@17780 0101bb08-14d6-0310-b084-bc0e0c8e3800

Distrotech/libtheora,Distrotech/libtheora,KTXSoftware/theora,KTXSoftware/theora,Distrotech/libtheora,Distrotech/libtheora,KTXSoftware/theora,KTXSoftware/theora,KTXSoftware/theora,Distrotech/libtheora