Use uint8_t for CachedMetadata

Historically Blink uses const char* for binary data but it doesn't fit
well with mojo IPCs. Convert const char* to uint8_t.

Bug: 915081
Change-Id: Ic0c0719d3eb3c3b72604ad6913a963c552da0dbc
Reviewed-on: https://chromium-review.googlesource.com/c/1390030
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618899}
43 files changed