Add operator== to CSSAnimationData.

This patch adds an operator== to CSSAnimationData that is used by
ComputedStyle to check equality for style resolve. Note this is
different to a full, memberwise equality.

BUG=628043

Review-Url: https://codereview.chromium.org/2904443002
Cr-Commit-Position: refs/heads/master@{#474241}
2 files changed