Don't call cancelAnimations() in RenderObject::willBeDestroyed() when no associate frame

This patch makes RenderObject::willBeDestroyed() not to do null dref for RenderObject::animation() call, which is frame()->animation(), by checking frame() returns non-null.

Note: Another patch will update src/tools/valgrind/tsan/suppressions.txt once this patch rolled into chromium DEPS; https://src.chromium.org/viewvc/chrome?view=rev&revision=225690

BUG=299647
TEST=fullscreen/fullscreen-child-not-allowed-crash.html; valgrind
R=morrita@chromium.org

Review URL: https://codereview.chromium.org/26648002

git-svn-id: svn://svn.chromium.org/blink/trunk@159204 bbb929c8-8fbe-4397-9dbb-9b2b20218538