Avoid the possibility to read out-of-bounds of a static global array in Vorbis

Avoid the possibility to read out-of-bounds of a static global array in Vorbis
decoding.

BUG=100543
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=106621

[Chris Evans, 2011-10-20 22:39:09]

(Array in question is 256 elements in size so patch makes clever use of type
system to clamp range without affecting performance in this sensitive area)

[rbultje1, 2011-10-20 22:42:59]

On 2011/10/20 22:39:09, Chris Evans wrote:
> (Array in question is 256 elements in size so patch makes clever use of type
> system to clamp range without affecting performance in this sensitive area)

I haven't looked very closely, but the caller which provides the invalid value
might still be considered buggy. Then again, regardless, if we want to guarantee
that the value is in the [0,255] range, then this patch is correct regardless of
whether the calling function is buggy. As such, LGTM.

Ronald

[scherkus (not reviewing), 2011-10-21 00:37:36]

ditto on LGTM / win binaries