Update timestmap of file only when content is changed

This can reduce build steps in incremental build.

Bug: 810298
Change-Id: I8ef6c3aa908f5d6e2e8c57edf8d29ed80a0d1993
Reviewed-on: https://chromium-review.googlesource.com/1126892
Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573483}
1 file changed