[SVG] Remove a couple of redundant hashmap look-ups.

No need for a separate contains() check - HashMap remove/take can handle
missing elements just fine.

R=pdr@chromium.org,schenney@chromium.org

Review URL: https://codereview.chromium.org/26725002

git-svn-id: svn://svn.chromium.org/blink/trunk@159264 bbb929c8-8fbe-4397-9dbb-9b2b20218538