ui: Cleanup class/struct forward declarations

extensions/browser/updater/update_install_shim.h

Index: extensions/browser/updater/update_install_shim.h
diff --git a/extensions/browser/updater/update_install_shim.h b/extensions/browser/updater/update_install_shim.h
index 518866a6062c2fd316621bde2bc2d30a03f3fb02..e6e9d93d038c65c406e971956851dfe5b466a65d 100644
--- a/extensions/browser/updater/update_install_shim.h
+++ b/extensions/browser/updater/update_install_shim.h
@@ -44,8 +44,8 @@ class UpdateInstallShim : public update_client::CrxInstaller {
 
   // This is called when a new version of an extension is unpacked at
   // |unpack_path| and is ready for install.
-  bool Install(const base::DictionaryValue& manifest,
-               const base::FilePath& unpack_path) override;
+  CrxInstaller::Result Install(const base::DictionaryValue& manifest,
+                               const base::FilePath& unpack_path) override;
 
   // This is called by the generic differential update code in the
   // update_client to provide the path to an existing file in the current