Remove some unused functions in RenderStyle
Remove some unused functions in RenderStyle

Trivial patch, found while investigating another issue. This patch
removes resetMargin and resetBorderRadius.

Review URL: https://codereview.chromium.org/337043002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@176258 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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