Use type-safe events for DeviceModeModel
Use type-safe events for DeviceModeModel

Bug: 1228674
Change-Id: I13b75b2297baca401936659366dc31124cc57edb
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/3094426
Commit-Queue: Kateryna Prokopenko <04b7d4bdbd93555cee90f085bb91b72524d21fca@google.com>
Reviewed-by: Simon Zünd <38944668e9e2ca98ccd0275b53370f90fa55c113@chromium.org>

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