tools/gn: Remove code for forward_dependent_configs_from variable.

This patch removes the supporting code for this variable, which is
deprecated. Before that all the projects using this variable were
updated and its usage were either updated to 'public_deps' or removed.

BUG=None
R=brettw@chromium.org

Review URL: https://codereview.chromium.org/1375023003

Cr-Original-Commit-Position: refs/heads/master@{#353144}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b445e7ccd70f09e53a6c93dee8a269d6bf7ee6f0
16 files changed
tree: d2b360cbe9e8d40324490aa293ff4957f4e90d3a
  1. tools/