Make dual screen support default
Make dual screen support default

Based on user study, setting this experiment default on may reduce
confusion and encourage more usage.

Change-Id: I29206cdf08725f51c26104b53da1482b751689d6
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2618641
Commit-Queue: Songtao Xia <efb39a3e57dd0e7c4fd137171d5e7a3f041d1da6@microsoft.com>
Reviewed-by: Yang Guo <1cf0af8245a3a17a632a2c73531392b0f9761c76@chromium.org>

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