Add support for uninstalling components and use it in SupervisedUserWhitelistInstaller.

components/update_client/update_client.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_UPDATE_CLIENT_UPDATE_CLIENT_H_
 #define COMPONENTS_UPDATE_CLIENT_UPDATE_CLIENT_H_
 
 #include <stdint.h>
 #include <string>
 #include <vector>
@@ skipping 27 matching lines @@
   virtual bool Install(const base::DictionaryValue& manifest,
                        const base::FilePath& unpack_path) = 0;
 
   // Set |installed_file| to the full path to the installed |file|. |file| is
   // the filename of the file in this component's CRX. Returns false if this is
   // not possible (the file has been removed or modified, or its current
   // location is unknown). Otherwise, returns true.
   virtual bool GetInstalledFile(const std::string& file,
                                 base::FilePath* installed_file) = 0;
 
+  // Called by the component updater when a component has been unregistered and
+  // all versions should be uninstalled from disk. Returns true if
+  // uninstallation is supported, false otherwise.
+  virtual bool Uninstall() = 0;
+
  protected:
   friend class base::RefCountedThreadSafe<ComponentInstaller>;
 
   virtual ~ComponentInstaller() {}
 };
 
 // Describes a particular component that can be installed or updated. This
 // structure is required to register a component with the component updater.
 // |pk_hash| is the SHA256 hash of the component's public key. If the component
 // is to be installed then version should be "0" or "0.0", else it should be
 // the current version. |fingerprint|, and |name| are optional.
 // |allow_background_download| specifies that the component can be background
 // downloaded in some cases. The default for this value is |true| and the value
 // can be overriden at the registration time. This is a temporary change until
 // the issue 340448 is resolved.
 struct CrxComponent {
   std::vector<uint8_t> pk_hash;
   scoped_refptr<ComponentInstaller> installer;
   Version version;
   std::string fingerprint;
   std::string name;
   bool allow_background_download;
   CrxComponent();
   ~CrxComponent();
 };
 
 }  // namespace update_client
 
 #endif  // COMPONENTS_UPDATE_CLIENT_UPDATE_CLIENT_H_