Clear site data through NetworkContextClient

When Clear-Site-Data header is received, call the OnClearSiteData()
method of NetworkContextClient instead of NetworkServiceClient because
NetworkContextClient always has a BrowserContext associated.

Bug: 952723
Change-Id: I8aff6bbd8eb9486379694d30c731974f24f86d50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1604469
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Ting Shao <ting.shao@intel.com>
Cr-Commit-Position: refs/heads/master@{#661162}
10 files changed