Add support for uninstalling components and use it in SupervisedUserWhitelistInstaller.

components/component_updater/default_component_installer.h

Index: components/component_updater/default_component_installer.h
diff --git a/components/component_updater/default_component_installer.h b/components/component_updater/default_component_installer.h
index 120d3a5de8cd44ae484120ee7633aa326e7661cd..83b4b092fde90e0aaeba1c9168f25bdb2fce2bd1 100644
--- a/components/component_updater/default_component_installer.h
+++ b/components/component_updater/default_component_installer.h
@@ -92,6 +92,10 @@ class DefaultComponentInstaller : public update_client::ComponentInstaller {
   // Registers the component for update checks and installs.
   void Register(ComponentUpdateService* cus);
 
+  // Unregisters the component for update checks and uninstalls it when the last
+  // reference to it is dropped.
+  void Unregister(ComponentUpdateService* cus);
+
   // Overridden from ComponentInstaller:
   void OnUpdateError(int error) override;
   bool Install(const base::DictionaryValue& manifest,
@@ -99,9 +103,9 @@ class DefaultComponentInstaller : public update_client::ComponentInstaller {
   bool GetInstalledFile(const std::string& file,
                         base::FilePath* installed_file) override;
 
+ private:
   ~DefaultComponentInstaller() override;
 
- private:
   base::FilePath GetInstallDirectory();
   bool InstallHelper(const base::DictionaryValue& manifest,
                      const base::FilePath& unpack_path,
@@ -114,6 +118,7 @@ class DefaultComponentInstaller : public update_client::ComponentInstaller {
   scoped_ptr<base::DictionaryValue> current_manifest_;
   scoped_ptr<ComponentInstallerTraits> installer_traits_;
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
+  bool should_uninstall_on_destruction_;
 
   // Used to post responses back to the main thread. Initialized on the main
   // loop but accessed from the task runner.