Remove support for old-style Mojo JS bindings.

Bug: 699569, 718047
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I3e2d9e55cac52b392bd31c96c51cc94a361b618b
Reviewed-on: https://chromium-review.googlesource.com/809545
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Yuzhu Shen <yzshen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522193}
85 files changed