Move data use measurement to DataUseNetworkDelegate

Currently data_use_measurement hooks to ChromeNetworkDelegate. It is more
appropriate to hook to DataUseNetworkDelegate, since getting web content
observer events other UI events will be easier (in future CLs) from
DataUseAscriber.

BUG=648808

Review-Url: https://codereview.chromium.org/2462983003
Cr-Commit-Position: refs/heads/master@{#432910}
28 files changed