Devirtualize SerializedScriptValue's destructor
Devirtualize SerializedScriptValue's destructor

Devirtualize SerializedScriptValue's destructor to avoid creating an
unnecessary vtable. SerializedScriptValue is never subclassed nor
does it have any virtual function.

BUG=

Review URL: https://codereview.chromium.org/40733002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@160477 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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