GitLab

https://chromium-review.googlesource.com/c/catapult/+/1961011 makes it so that
if you do no specify a --webview-embedder-apk flag then we will use
WebLayerShellSystemWebView.apk for a weblayer browser.

It is also nicer not to explicit specify a flag for the reasons described
in
https://chromium.googlesource.com/chromium/src.git/+/c1324fa4ee0802370abbd624df217ef7b479180c

R=johnchen@chromium.org

Bug: 1028125
Change-Id: I01ac075f8ef92928ca9e15dbb665ea9ce8c95f77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1981068Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727484}