Move StyleBoxData.cpp to be inline in StyleBoxData.h.

This patch removes StyleBoxData.cpp, and moves all its contents to be
inline in StyleBoxData.h

This is prework for generating StyleBoxData.

BUG=628043

Review-Url: https://codereview.chromium.org/2857873003
Cr-Commit-Position: refs/heads/master@{#470868}
3 files changed