tools/gn: Remove code for forward_dependent_configs_from variable.

tools/gn/builder.cc

Index: tools/gn/builder.cc
diff --git a/tools/gn/builder.cc b/tools/gn/builder.cc
index ca11e888d353bd3d6c5168afe09580103711fab8..5548d2b4082c0d0dcfadf157fec8f8a318f5cf60 100644
--- a/tools/gn/builder.cc
+++ b/tools/gn/builder.cc
@@ -416,7 +416,6 @@ bool Builder::ResolveItem(BuilderRecord* record, Err* err) {
         !ResolveConfigs(&target->configs(), err) ||
         !ResolveConfigs(&target->all_dependent_configs(), err) ||
         !ResolveConfigs(&target->public_configs(), err) ||
-        !ResolveForwardDependentConfigs(target, err) ||
         !ResolveToolchain(target, err))
       return false;
   } else if (record->type() == BuilderRecord::ITEM_CONFIG) {
@@ -477,37 +476,6 @@ bool Builder::ResolveConfigs(UniqueVector<LabelConfigPair>* configs, Err* err) {
   return true;
 }
 
-// "Forward dependent configs" should refer to targets in the deps that should
-// have their configs forwarded.
-bool Builder::ResolveForwardDependentConfigs(Target* target, Err* err) {
-  const UniqueVector<LabelTargetPair>& configs =
-      target->forward_dependent_configs();
-
-  // Assume that the lists are small so that brute-force n^2 is appropriate.
-  for (const auto& config : configs) {
-    for (const auto& dep_pair : target->GetDeps(Target::DEPS_LINKED)) {
-      if (config.label == dep_pair.label) {
-        DCHECK(dep_pair.ptr);  // Should already be resolved.
-        // UniqueVector's contents are constant so uniqueness is preserved, but
-        // we want to update this pointer which doesn't change uniqueness
-        // (uniqueness in this vector is determined by the label only).
-        const_cast<LabelTargetPair&>(config).ptr = dep_pair.ptr;
-        break;
-      }
-    }
-    if (!config.ptr) {
-      *err = Err(target->defined_from(),
-          "Target in forward_dependent_configs_from was not listed in the deps",
-          "This target has a forward_dependent_configs_from entry that was "
-          "not present in\nthe deps. A target can only forward things it "
-          "depends on. It was forwarding:\n  " +
-          config.label.GetUserVisibleName(false));
-      return false;
-    }
-  }
-  return true;
-}
-
 bool Builder::ResolveToolchain(Target* target, Err* err) {
   BuilderRecord* record = GetResolvedRecordOfType(
       target->settings()->toolchain_label(), target->defined_from(),