CodeHealth: Remove use of DictionaryValue::HasKey in /remoting

This change removes the use of `DictionaryValue::HasKey()`
and replaces with `Value::FindKey()`.

This CL was uploaded by git cl split.

R=garykac@chromium.org

Bug: 1187060
Change-Id: Ica914df2f412258f56395575ba2c4ce10bc18156
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2880292


Auto-Submit: Anastasiia N <anastasiian@chromium.org>
Commit-Queue: Gary Kacmarcik <garykac@chromium.org>
Reviewed-by: Gary Kacmarcik <garykac@chromium.org>
Cr-Commit-Position: refs/heads/master@{#880995}