[css-typed-om] merge constructor using optional keyword

merge constructor using optional keyword in CSSTransformValue
and CSSTranslation

Bug: 545318
Change-Id: I67fe1f7b8db1dd59689d6aa8c49938f48152c5f8
Reviewed-on: https://chromium-review.googlesource.com/763149
Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: Hwanseung Lee <hs1217.lee@samsung.com>
Cr-Commit-Position: refs/heads/master@{#515872}
2 files changed