DevTools: Mark the '== $0' hint as hidden
DevTools: Mark the '== $0' hint as hidden

In the elements panel, every selected element has a hint
about using $0 in the console. This is pretty noisey for a screen
reader user, and not very helpful.

Change-Id: I50985bb7b1289c90029a2e933911fa8e6f60f965
Reviewed-on: https://chromium-review.googlesource.com/1228993
Reviewed-by: Erik Luo <26192f5e05d23e5ee959014fb911d780e566545b@chromium.org>
Commit-Queue: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#591900}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 9a730cb01c5ffbec308d96949e4a2d47ac109422
ChromeDevTools/devtools-frontend,dart-archive/devtools-frontend,dart-archive/devtools-frontend,ChromeDevTools/devtools-frontend,dart-archive/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,dart-archive/devtools-frontend,dart-archive/devtools-frontend,ChromeDevTools/devtools-frontend,dart-archive/devtools-frontend