DevTools: Fix watch expressions editor margins
DevTools: Fix watch expressions editor margins

NOTRY=true
BUG=803399

Change-Id: If3bab9284ae13a97d8f3f84b10dc971da8f228fb
Reviewed-on: https://chromium-review.googlesource.com/1129462
Reviewed-by: Aleksey Kozyatinskiy <562acbea96970f508ad9f5cc9fc7c62d82dd3ef8@chromium.org>
Commit-Queue: Alexei Filippov <52e51c43e283548b762e3c9dd9a4600768db9fb4@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#573728}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 9cf21e0c6801d09032574ea225958fd1a34ad5c9
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