Add a UniqueVector class to GN

tools/gn/target_unittest.cc

Index: tools/gn/target_unittest.cc
diff --git a/tools/gn/target_unittest.cc b/tools/gn/target_unittest.cc
index f9a1f972a43c36ed9af20a51159b8b39b7bb6f66..9dcaf08e468ba3fa7db2f0f9a4c3b666b5982806 100644
--- a/tools/gn/target_unittest.cc
+++ b/tools/gn/target_unittest.cc
@@ -221,19 +221,19 @@ TEST_F(TargetTest, InheritLibs) {
   a.OnResolved();
 
   // C should have D in its inherited libs.
-  const std::set<const Target*>& c_inherited = c.inherited_libraries();
+  const UniqueVector<const Target*>& c_inherited = c.inherited_libraries();
   EXPECT_EQ(1u, c_inherited.size());
-  EXPECT_TRUE(c_inherited.find(&d) != c_inherited.end());
+  EXPECT_TRUE(c_inherited.IndexOf(&d) != static_cast<size_t>(-1));
 
   // B should have C and D in its inherited libs.
-  const std::set<const Target*>& b_inherited = b.inherited_libraries();
+  const UniqueVector<const Target*>& b_inherited = b.inherited_libraries();
   EXPECT_EQ(2u, b_inherited.size());
-  EXPECT_TRUE(b_inherited.find(&c) != b_inherited.end());
-  EXPECT_TRUE(b_inherited.find(&d) != b_inherited.end());
+  EXPECT_TRUE(b_inherited.IndexOf(&c) != static_cast<size_t>(-1));
+  EXPECT_TRUE(b_inherited.IndexOf(&d) != static_cast<size_t>(-1));
 
   // A should have B in its inherited libs, but not any others (the shared
   // library will include the static library and source set).
-  const std::set<const Target*>& a_inherited = a.inherited_libraries();
+  const UniqueVector<const Target*>& a_inherited = a.inherited_libraries();
   EXPECT_EQ(1u, a_inherited.size());
-  EXPECT_TRUE(a_inherited.find(&b) != a_inherited.end());
+  EXPECT_TRUE(a_inherited.IndexOf(&b) != static_cast<size_t>(-1));
 }