Report data use from renderer to browser page load metrics

Report the continuous data use to page load metrics in browser process
via the existing renderer -> browser PageLoadMetrics mojo.

Bug: 836029
Cq-Include-Trybots: luci.chromium.try:linux_mojo
Change-Id: I1c7b47eb41e13f9b72d087e3ca2c0a7096c11b29
Reviewed-on: https://chromium-review.googlesource.com/1042877
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: rajendrant <rajendrant@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574421}
27 files changed