ui: Cleanup class/struct forward declarations

chrome/browser/component_updater/sth_set_component_installer.cc

Index: chrome/browser/component_updater/sth_set_component_installer.cc
diff --git a/chrome/browser/component_updater/sth_set_component_installer.cc b/chrome/browser/component_updater/sth_set_component_installer.cc
index f6ac974ee3dd6071f89fbeaa57ace29b27826761..b1b06d3f2412e2093cb5565cd82b219c394528c1 100644
--- a/chrome/browser/component_updater/sth_set_component_installer.cc
+++ b/chrome/browser/component_updater/sth_set_component_installer.cc
@@ -65,10 +65,11 @@ bool STHSetComponentInstallerTraits::RequiresNetworkEncryption() const {
   return false;
 }
 
-bool STHSetComponentInstallerTraits::OnCustomInstall(
+update_client::CrxInstaller::Result
+STHSetComponentInstallerTraits::OnCustomInstall(
     const base::DictionaryValue& manifest,
     const base::FilePath& install_dir) {
-  return true;  // Nothing custom here.
+  return update_client::CrxInstaller::Result(0);  // Nothing custom here.
 }
 
 void STHSetComponentInstallerTraits::ComponentReady(