Fixed leaking data in WebThreadSafeData
Fixed leaking data in WebThreadSafeData

BUG=

Review URL: https://codereview.chromium.org/1205683002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@197765 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk