DevTools: Don't label top level completions as from the first prototype
DevTools: Don't label top level completions as from the first prototype

In an object like {abc: 123}, the property 'abc' was mistakenly labeled
as being from the Object prototype.

ScreenShot: https://i.imgur.com/bdIWNDt.png

Bug: none

Change-Id: I85aed6eaa6561afbc54f52115ec9bf539fd345eb
Reviewed-on: https://chromium-review.googlesource.com/c/1460180
Commit-Queue: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Reviewed-by: Erik Luo <26192f5e05d23e5ee959014fb911d780e566545b@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#630533}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 9746319d367067421d8cfabd83408fc478a90cea
ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend