Add support for uninstalling components and use it in SupervisedUserWhitelistInstaller.

chrome/browser/component_updater/pnacl/pnacl_component_installer.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/component_updater/pnacl/pnacl_component_installer.h"
 
 #include <stdint.h>
 #include <string>
 #include <vector>
 
@@ skipping 262 matching lines @@
                                                base::FilePath* installed_file) {
   if (current_version().Equals(Version(kNullVersion)))
     return false;
 
   *installed_file = GetPnaclBaseDirectory()
                         .AppendASCII(current_version().GetString())
                         .AppendASCII(file);
   return true;
 }
 
+bool PnaclComponentInstaller::Uninstall() {
+  return false;
+}
+
 CrxComponent PnaclComponentInstaller::GetCrxComponent() {
   CrxComponent pnacl_component;
   pnacl_component.version = current_version();
   pnacl_component.name = "pnacl";
   pnacl_component.installer = this;
   pnacl_component.fingerprint = current_fingerprint();
   SetPnaclHash(&pnacl_component);
 
   return pnacl_component;
 }
@@ skipping 82 matching lines @@
 }  // namespace component_updater
 
 namespace pnacl {
 
 bool NeedsOnDemandUpdate() {
   return base::subtle::NoBarrier_Load(
              &component_updater::needs_on_demand_update) != 0;
 }
 
 }  // namespace pnacl