suppress user-after-free from blink::WebLocalFrameImpl::setFrameWidget
suppress user-after-free from blink::WebLocalFrameImpl::setFrameWidget

TBR=dcheng@chromium.org, dpranke@chromium.org
BUG=509508
NOTRY=true

Review URL: https://codereview.chromium.org/1233803002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#338467}

axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,Chilledheart/chromium,Just-D/chromium-1,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,Just-D/chromium-1,Chilledheart/chromium,Just-D/chromium-1,Chilledheart/chromium,Pluto-tv/chromium-crosswalk