Use Time class for response time in Blink instead of int64.

After https://crrev.com/2543663002 we can use Time class in Blink.

BUG=732214

Change-Id: I6ef34fd8d342c7776c4fbe69837f727bedb131a1
Reviewed-on: https://chromium-review.googlesource.com/547820
Reviewed-by: Yuta Kitamura <yutak@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#482260}
17 files changed