fixup! OnionSoup: Migrate IPC message handler to Mojo in Android's RendererDateTimePicker

The original CL has used AscII() in TypeConverter for blink::WebDateTimeSuggestion.
It can contain arbitrary characters. This CL changes string type with mojo_base.mojom.String16
to fix the issue as well as to reduce UTF string type conversions.

Bug: 950157
Change-Id: I49d4bff5661700bb3439212ee9fe6143a4923ba8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583026
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#653953}
3 files changed