If more than 60 frames are created and not returned, the implementation will crash. I420BufferPool are currently used by the VP8 decoder, Quality scaler and VideoFrameFactory. BUG=b/31390397 NOTRY=true // Because of failing gclient runhooks on some bots Review-Url: https://codereview.webrtc.org/2370653003 Cr-Commit-Position: refs/heads/master@{#14395}