Add a UniqueVector class to GN

tools/gn/header_checker.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/header_checker.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/file_util.h"
@@ skipping 46 matching lines @@
       !values.cflags_cc().empty() ||
       !values.cflags_objc().empty() ||
       !values.cflags_objcc().empty() ||
       !values.defines().empty() ||
       !values.include_dirs().empty();
 }
 
 // Returns true if the given target has any direct dependent configs with
 // compiler settings in it.
 bool HasDirectDependentCompilerSettings(const Target* target) {
-  const LabelConfigVector& direct = target->direct_dependent_configs();
+  const UniqueVector<LabelConfigPair>& direct =
+      target->direct_dependent_configs();
   for (size_t i = 0; i < direct.size(); i++) {
     if (ConfigHasCompilerSettings(direct[i].ptr))
       return true;
   }
   return false;
 }
 
 // Given a reverse dependency chain where the target chain[0]'s dependent
 // configs don't apply to chain[end], returns the string describing the error.
 // The problematic index is the target where the dependent configs were lost.
@@ skipping 346 matching lines @@
     return true;
 
   // Check the middle configs to make sure they're either groups or configs
   // are forwarded.
   for (size_t i = 1; i < chain.size() - 1; i++) {
     if (chain[i]->output_type() == Target::GROUP)
       continue;  // This one is OK, skip to next one.
 
     // The forward list on this target should have contained in it the target
     // at the next lower level.
-    const LabelTargetVector& forwarded = chain[i]->forward_dependent_configs();
+    const UniqueVector<LabelTargetPair>& forwarded =
+        chain[i]->forward_dependent_configs();
     if (std::find_if(forwarded.begin(), forwarded.end(),
                      LabelPtrPtrEquals<Target>(chain[i - 1])) ==
         forwarded.end()) {
       *problematic_index = i;
       return false;
     }
   }
 
   return true;
 }