add to spellproc_warrior.cpp
class TasteOfBloodSpellProc : public SpellProc
{
    SPELL_PROC_FACTORY_FUNCTION( TasteOfBloodSpellProc );

    bool CanProc(Unit* victim, SpellEntry* CastingSpell)
    {
        if( CastingSpell == NULL )
            return false;
        if( CastingSpell->NameHash != SPELL_HASH_REND )
            return false;
        return true;
    }

    bool DoEffect(Unit* victim, SpellEntry* CastingSpell, uint32 flag, uint32 dmg, uint32 abs, int* dmg_overwrite, uint32 weapon_damage_type)
    {
        if(!(flag & PROC_ON_SPELL_HIT))
            return true;
        return false;
    }
};
add into SpellProcMgr::SetupWarrior()
AddByNameHash(SPELL_HASH_TASTE_OF_BLOOD, &TasteOfBloodSpellProc::Create);