GitLab

Create a message that will be used by JS message channels to pass data
back into the Webview client.

Bug: b/141864193
Test: Compiled
Change-Id: Iada17bc8f3cf1276f3a59813406f67bc43af8247
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1850363Reviewed-by: Alex Sakhartchouk <alexst@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704613}