Add a UniqueVector class to GN

tools/gn/command_desc.cc

 // Copyright (c) 2013 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 <algorithm>
 #include <set>
 #include <sstream>
 
 #include "base/command_line.h"
 #include "tools/gn/commands.h"
@@ skipping 232 matching lines @@
   if (display_header)
     OutputString("\n" + heading + " (in order applying):\n");
 
   Label toolchain_label = target->label().GetToolchainLabel();
   for (size_t i = 0; i < configs.size(); i++) {
     OutputString("  " +
         configs[i].label.GetUserVisibleName(toolchain_label) + "\n");
   }
 }
 
+void PrintConfigsVector(const Target* target,
+                        const UniqueVector<LabelConfigPair>& configs,
+                        const std::string& heading,
+                        bool display_header) {
+  if (configs.empty())
+    return;
+
+  // Don't sort since the order determines how things are processed.
+  if (display_header)
+    OutputString("\n" + heading + " (in order applying):\n");
+
+  Label toolchain_label = target->label().GetToolchainLabel();
+  for (size_t i = 0; i < configs.size(); i++) {
+    OutputString("  " +
+        configs[i].label.GetUserVisibleName(toolchain_label) + "\n");
+  }
+}
+
 void PrintConfigs(const Target* target, bool display_header) {
-  PrintConfigsVector(target, target->configs(), "configs", display_header);
+  PrintConfigsVector(target, target->configs().vector(), "configs",
+                     display_header);
 }
 
 void PrintDirectDependentConfigs(const Target* target, bool display_header) {
   PrintConfigsVector(target, target->direct_dependent_configs(),
                      "direct_dependent_configs", display_header);
 }
 
 void PrintAllDependentConfigs(const Target* target, bool display_header) {
   PrintConfigsVector(target, target->all_dependent_configs(),
                      "all_dependent_configs", display_header);
@@ skipping 380 matching lines @@
   // so always display them, even for groups and such.
   PrintLibs(target, true);
   PrintLibDirs(target, true);
 
   PrintDeps(target, true);
 
   return 0;
 }
 
 }  // namespace commands