Make SVGProperty RefCountedGarbageCollected to prepare for oilpan.
Make SVGProperty RefCountedGarbageCollected to prepare for oilpan.

SVGProperty will be GarbageCollected at the end, but I'm making this RefCountedGarbageCollected first so we can work on this incrementally.

BUG=357163

Review URL: https://codereview.chromium.org/282753006

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@173967 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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