Convert //extensions/browser from scoped_ptr to std::unique_ptr

extensions/browser/mock_extension_system.cc

Index: extensions/browser/mock_extension_system.cc
diff --git a/extensions/browser/mock_extension_system.cc b/extensions/browser/mock_extension_system.cc
index 6658832e7449b355384eb35a0b062030e3c784d0..621fe93a7117e13142ea98b12c4ff6c9498ac3e7 100644
--- a/extensions/browser/mock_extension_system.cc
+++ b/extensions/browser/mock_extension_system.cc
@@ -71,9 +71,9 @@ ContentVerifier* MockExtensionSystem::content_verifier() {
   return nullptr;
 }
 
-scoped_ptr<ExtensionSet> MockExtensionSystem::GetDependentExtensions(
+std::unique_ptr<ExtensionSet> MockExtensionSystem::GetDependentExtensions(
     const Extension* extension) {
-  return scoped_ptr<ExtensionSet>();
+  return std::unique_ptr<ExtensionSet>();
 }
 
 void MockExtensionSystem::InstallUpdate(const std::string& extension_id,