Add a UniqueVector class to GN

tools/gn/target_generator.cc

Index: tools/gn/target_generator.cc
diff --git a/tools/gn/target_generator.cc b/tools/gn/target_generator.cc
index 12d09fca1527092d16ff2b249a47e72ce739fe14..0affb94abb718ddae7c974cd090be81e6bb81df1 100644
--- a/tools/gn/target_generator.cc
+++ b/tools/gn/target_generator.cc
@@ -239,11 +239,11 @@ void TargetGenerator::FillOutputs() {
 }
 
 void TargetGenerator::FillGenericConfigs(const char* var_name,
-                                         LabelConfigVector* dest) {
+                                         UniqueVector<LabelConfigPair>* dest) {
   const Value* value = scope_->GetValue(var_name, true);
   if (value) {
-    ExtractListOfLabels(*value, scope_->GetSourceDir(),
-                        ToolchainLabelForScope(scope_), dest, err_);
+    ExtractListOfUniqueLabels(*value, scope_->GetSourceDir(),
+                              ToolchainLabelForScope(scope_), dest, err_);
   }
 }
 
@@ -260,8 +260,8 @@ void TargetGenerator::FillForwardDependentConfigs() {
   const Value* value = scope_->GetValue(
       variables::kForwardDependentConfigsFrom, true);
   if (value) {
-    ExtractListOfLabels(*value, scope_->GetSourceDir(),
-                        ToolchainLabelForScope(scope_),
-                        &target_->forward_dependent_configs(), err_);
+    ExtractListOfUniqueLabels(*value, scope_->GetSourceDir(),
+                              ToolchainLabelForScope(scope_),
+                              &target_->forward_dependent_configs(), err_);
   }
 }