Implement ExtensionLocalizationPeer with data pipe

Previously ExtensionLocalizationPeer::OnStartLoadingResponseBody() passed the
pipe through the |original_peer_|. As we are moving body transfer from
RequestPeer::OnReceivedData to OnStartLoadingResponseBody, this CL implements
OnStartloadingResponseBody() and the following logic.

Bug: 907793
Change-Id: If85d788084ca089fd34ba9b17b016240ecd29214
Reviewed-on: https://chromium-review.googlesource.com/c/1358311
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616461}
3 files changed