ozone: Fix chromium-style warnings in rendering_helper.cc
ozone: Fix chromium-style warnings in rendering_helper.cc

This fixes the linux_chromium_chromeos_ozone_rel_ng bot:

../../content/common/gpu/media/rendering_helper.cc:105:31: error: [chromium-style] Overriding method must be marked with 'override' or 'final'.
  virtual ~StubOzoneDelegate() {}
                              ^
                               override

TBR=posciak (red build)
NOTRY=true
BUG=none
TEST=linux_chromium_chromeos_ozone_rel_ng trybot

Review URL: https://codereview.chromium.org/875573004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#313763}

ltilve/chromium,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,chuan9/chromium-crosswalk,ltilve/chromium,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,fujunwei/chromium-crosswalk,Fireblend/chromium-crosswalk,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,ltilve/chromium,Pluto-tv/chromium-crosswalk,ltilve/chromium,Chilledheart/chromium,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,ltilve/chromium,Pluto-tv/chromium-crosswalk,ltilve/chromium,Chilledheart/chromium,Just-D/chromium-1,chuan9/chromium-crosswalk,Just-D/chromium-1,ltilve/chromium,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,ltilve/chromium,ltilve/chromium,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,Just-D/chromium-1,Fireblend/chromium-crosswalk,Just-D/chromium-1,chuan9/chromium-crosswalk,Chilledheart/chromium