Convert //tools to use std::unique_ptr

tools/gn/string_utils_unittest.cc

Index: tools/gn/string_utils_unittest.cc
diff --git a/tools/gn/string_utils_unittest.cc b/tools/gn/string_utils_unittest.cc
index 570997ff1b72bd2f1acbb6c60e9e946dc8444298..eb021a8d5c7eb46ac6967766a5da058baa2bd4a5 100644
--- a/tools/gn/string_utils_unittest.cc
+++ b/tools/gn/string_utils_unittest.cc
@@ -23,7 +23,8 @@ bool CheckExpansionCase(const char* input, const char* expected, bool success) {
   scope.SetValue("onestring", Value(nullptr, "one"), nullptr);
 
   // Nested scope called "onescope" with a value "one" inside it.
-  scoped_ptr<Scope> onescope(new Scope(static_cast<const Settings*>(nullptr)));
+  std::unique_ptr<Scope> onescope(
+      new Scope(static_cast<const Settings*>(nullptr)));
   onescope->SetValue("one", Value(nullptr, one), nullptr);
   scope.SetValue("onescope", Value(nullptr, std::move(onescope)), nullptr);