Componentize component_updater: Replace content::BrowserThread usage with task runners

chrome/browser/component_updater/component_updater_service.h

 // Copyright 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.
 
 #ifndef CHROME_BROWSER_COMPONENT_UPDATER_COMPONENT_UPDATER_SERVICE_H_
 #define CHROME_BROWSER_COMPONENT_UPDATER_COMPONENT_UPDATER_SERVICE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
+#include "base/memory/ref_counted.h"
 #include "base/version.h"
 #include "url/gurl.h"
 
 class ComponentsUI;
 
 namespace base {
 class DictionaryValue;
 class FilePath;
+class SequencedTaskRunner;
 }
 
 namespace net {
 class URLRequestContextGetter;
 class URLRequest;
 }
 
 namespace content {
 class ResourceThrottle;
 }
 
 namespace component_updater {
 
 class Configurator;
 class OnDemandUpdater;
 
 // Component specific installers must derive from this class and implement
 // OnUpdateError() and Install(). A valid instance of this class must be
 // given to ComponentUpdateService::RegisterComponent().
 class ComponentInstaller {
  public:
-  // Called by the component updater on the UI thread when there was a
+  // Called by the component updater on the main thread when there was a
   // problem unpacking or verifying the component. |error| is a non-zero
   // value which is only meaningful to the component updater.
   virtual void OnUpdateError(int error) = 0;
 
   // Called by the component updater when a component has been unpacked
   // and is ready to be installed. |manifest| contains the CRX manifest
   // json dictionary and |unpack_path| contains the temporary directory
-  // with all the unpacked CRX files.
+  // with all the unpacked CRX files. This method may be called from
+  // a thread other than the main thread.
   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;
 
@@ skipping 29 matching lines @@
 // to package extensions. To the update service each component is identified
 // by its public key hash (CrxComponent::pk_hash). If there is an update
 // available and its version is bigger than (CrxComponent::version), it will
 // be downloaded, verified and unpacked. Then component-specific installer
 // ComponentInstaller::Install (of CrxComponent::installer) will be called.
 //
 // During the normal operation of the component updater some specific
 // notifications are fired, like COMPONENT_UPDATER_STARTED and
 // COMPONENT_UPDATE_FOUND. See notification_type.h for more details.
 //
-// All methods are safe to call ONLY from chrome's UI thread.
+// All methods are safe to call ONLY from the browser's main thread.
 class ComponentUpdateService {
  public:
   enum Status { kOk, kReplaced, kInProgress, kError };
 
   // Defines an interface to observe ComponentUpdateService. It provides
   // notifications when state changes occur for the service or for the
   // registered components.
   class Observer {
    public:
     enum Events {
@@ skipping 51 matching lines @@
   // before calling Start().
   virtual Status RegisterComponent(const CrxComponent& component) = 0;
 
   // Returns a list of registered components.
   virtual std::vector<std::string> GetComponentIDs() const = 0;
 
   // Returns an interface for on-demand updates. On-demand updates are
   // proactively triggered outside the normal component update service schedule.
   virtual OnDemandUpdater& GetOnDemandUpdater() = 0;
 
+  // Returns a task runner suitable for use by component installers.
+  virtual scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner() = 0;
+
   virtual ~ComponentUpdateService() {}
 
  private:
   // Returns details about registered component in the |item| parameter. The
   // function returns true in case of success and false in case of errors.
   virtual bool GetComponentDetails(const std::string& component_id,
                                    CrxUpdateItem* item) const = 0;
 
   friend class ::ComponentsUI;
   FRIEND_TEST_ALL_PREFIXES(ComponentUpdaterTest, ResourceThrottleLiveNoUpdate);
@@ skipping 30 matching lines @@
       const std::string& component_id) = 0;
 };
 
 // Creates the component updater. You must pass a valid |config| allocated on
 // the heap which the component updater will own.
 ComponentUpdateService* ComponentUpdateServiceFactory(Configurator* config);
 
 }  // namespace component_updater
 
 #endif  // CHROME_BROWSER_COMPONENT_UPDATER_COMPONENT_UPDATER_SERVICE_H_