Clean up threading model of external extension providers

chrome/browser/extensions/external_extension_provider_interface.h

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_H_
-#define CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_H_
+#ifndef CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_INTERFACE_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_INTERFACE_H_
 #pragma once
 
+#include <vector>
+
+#include "base/linked_ptr.h"
 #include "chrome/common/extensions/extension.h"
 
 class FilePath;
 class Version;
 
 // This class is an abstract class for implementing external extensions
 // providers.
-class ExternalExtensionProvider {
+class ExternalExtensionProviderInterface {
  public:
   // ExternalExtensionProvider uses this interface to communicate back to the
   // caller what extensions are registered, and which |id|, |version| and |path|
   // they have. See also VisitRegisteredExtension below. Ownership of |version|
   // is not transferred to the visitor.
-  class Visitor {
+  class VisitorInterface {
    public:
      virtual void OnExternalExtensionFileFound(
          const std::string& id,
          const Version* version,
          const FilePath& path,
          Extension::Location location) = 0;
 
      virtual void OnExternalExtensionUpdateUrlFound(
          const std::string& id,
          const GURL& update_url,
          Extension::Location location) = 0;
 
+     // Called after all the external extensions have been reported through
+     // the above two methods.
+     virtual void OnExternalProviderReady() = 0;
+
    protected:
-     virtual ~Visitor() {}
+     virtual ~VisitorInterface() {}
   };
 
-  virtual ~ExternalExtensionProvider() {}
+  virtual ~ExternalExtensionProviderInterface() {}
 
-  // Enumerate registered extension, calling OnExternalExtensionFound on
-  // the |visitor| object for each registered extension found. |ids_to_ignore|
-  // contains a list of extension ids that should not result in a call back.
-  virtual void VisitRegisteredExtension(Visitor* visitor) const = 0;
+  // The visitor (ExtensionsService) calls this function before it goes away.
+  virtual void ServiceShutdown() = 0;
+
+  // Enumerate registered extensions, calling
+  // OnExternalExtension(File|UpdateUrl)Found on the |visitor| object for each
+  // registered extension found.
+  virtual void VisitRegisteredExtension() const = 0;
 
   // Test if this provider has an extension with id |id| registered.
   virtual bool HasExtension(const std::string& id) const = 0;
 
   // Gets details of an extension by its id.  Output params will be set only
   // if they are not NULL.  If an output parameter is not specified by the
   // provider type, it will not be changed.
   // This function is no longer used outside unit tests.
   virtual bool GetExtensionDetails(const std::string& id,
                                    Extension::Location* location,
                                    scoped_ptr<Version>* version) const = 0;
+
+  // Determines if this provider had loaded the list of external extensions
+  // from its source.
+  virtual bool IsReady() = 0;
 };
 
-#endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_H_
+typedef std::vector<linked_ptr<ExternalExtensionProviderInterface> >
+    ProviderCollection;
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_INTERFACE_H_