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 8a39993bb970d0c6961df4b265692808cf734dbc..7247891bba59d03cf1f38d0b9d5fb25f083618d6 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,
@@ -115,6 +119,7 @@ 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.