Remove PingLoaderImpl

This CL retires PingLoaderImpl. Existing customers will use ResouceFetcher
instead.

Bug: 695939
Change-Id: I93738be6e6000e3dc190abca38991cffbe503c80
Reviewed-on: https://chromium-review.googlesource.com/554530
Reviewed-by: Takeshi Yoshino <tyoshino@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483720}
2 files changed