Implement an API to allow passing an "ap" parameter to component updates.

components/component_updater/default_component_installer.h

 // Copyright 2014 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_COMPONENT_UPDATER_DEFAULT_COMPONENT_INSTALLER_H_
 #define COMPONENTS_COMPONENT_UPDATER_DEFAULT_COMPONENT_INSTALLER_H_
 
 #include <stdint.h>
 #include <string>
 #include <vector>
@@ skipping 65 matching lines @@
 
   // Returns the directory that the installer will place versioned installs of
   // the component into.
   virtual base::FilePath GetBaseDirectory() const = 0;
 
   // Returns the component's SHA2 hash as raw bytes.
   virtual void GetHash(std::vector<uint8_t>* hash) const = 0;
 
   // Returns the human-readable name of the component.
   virtual std::string GetName() const = 0;
+
+  // Returns the additional parameters to be used in the update checks for
+  // this component. A compatible server may use this attribute to negotiate
+  // special update rules when issuing an update response.
+  // The current implementation restricts ap to ^([-+_=a-zA-Z0-9]{0,256})$
+  virtual std::string GetAp() const = 0;
 };
 
 // A DefaultComponentInstaller is intended to be final, and not derived from.
 // Customization must be provided by passing a ComponentInstallerTraits object
 // to the constructor.
 class DefaultComponentInstaller : public update_client::CrxInstaller {
  public:
   DefaultComponentInstaller(
       scoped_ptr<ComponentInstallerTraits> installer_traits);
 
@@ skipping 34 matching lines @@
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultComponentInstaller);
 };
 
 }  // namespace component_updater
 
 #endif  // COMPONENTS_COMPONENT_UPDATER_DEFAULT_COMPONENT_INSTALLER_H_