Add DEPS rules for //chromeos/lacros.

The directory is the equivalent of Win32 on Windows and Cocoa on macOS.
It should not include //content or //chrome.

Change-Id: I057a77b2c4a0f4c72aee4218ce743d12c6211bd7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2432126
Commit-Queue: Erik Chen <erikchen@chromium.org>
Auto-Submit: Erik Chen <erikchen@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810721}

chromeos/lacros/DEPS

+# This directory must not depend on //content or //chrome. This contains
+# low-level ChromeOS system APIs for lacros. It's the equivalent of Win32 for
+# Windows or Cocoa for macOS.
+include_rules = [
+  "-chrome",
+  "-content",
+]