Revert 168617 "Oilpan: Fix tracing of KeyframeVector in Composit..."

It broke build of Linux ChromiumOS Builder.

> Oilpan: Fix tracing of KeyframeVector in CompositorAnimationsTest.
> 
> R=haraken@chromium.org, oilpan-reviews@chromium.org
> BUG=
> 
> Review URL: https://codereview.chromium.org/183923038

TBR=ager@chromium.org

Review URL: https://codereview.chromium.org/180033007

git-svn-id: svn://svn.chromium.org/blink/trunk@168637 bbb929c8-8fbe-4397-9dbb-9b2b20218538