Refactor loading out of ExtensionService.

chrome/browser/extensions/component_loader.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.

[Aaron Boodman, 2011/10/28 22:21:58]

What about this idea for a simplification:

class ComponentLoader {
 public:
  // No need to expose ComponentExtensionInfo struct.
  Add(const std::string& manifest, const FilePath&);
  Remove(const std::string& manifest);

  // When ES is NULL, calls to Add() and Remove() are queued.
  // When this method is called, all queued additions are loaded. 
  // If Add() or Remove() are called after this is set, they are
  // delegate through to ES immediately.
  SetExtensionService(ExtensionService*);
}

[Yoyo Zhou, 2011/10/31 21:58:15]

Yeah, this is unnecessary. I'll get rid of this right now.
So we'd associate this with the Profile then. Okay.
As I understand it, the reasons for having this registering are twofold:
1. having component extensions available at startup,
2. not forgetting about them when we ReloadExtensions() (only in tests).

Sounds like this addresses issue 1 but not 2. Maybe for that, the right thing to
do is handle them specially when we do ReloadExtensions/UnloadAllExtensions.

[Aaron Boodman, 2011/10/31 22:33:25]

I think it needs to be a property of ES, at least for now, because it doesn't
make sense to duplicate in Incognito profiles.
In that case, you could keep track of them either way in ComponentLoader. I'm
just trying to find a way to get rid of the weird duplicate Register and Add
methods.

[Yoyo Zhou, 2011/11/01 21:50:57]

You can't do this if it's a property of ExtensionService.
"When ES is null..." Actually, we register when ES has been created but not
initialized. I think I should use ES::is_ready() for this. Here's my plan:

Case 1 (startup):
Add() registers. If ES is initialized, it also loads. Otherwise it doesn't load.
ES::Init calls LoadAll() which loads everything. A slight problem here is the
guarantee that things are loaded eventually isn't built into ComponentLoader.

Remove() unregisters and unloads.

Case 2 (reload all):
ES::ReloadAll calls LoadAll().

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_COMPONENT_LOADER_H_
+#define CHROME_BROWSER_EXTENSIONS_COMPONENT_LOADER_H_
+#pragma once
+
+#include "base/file_path.h"
+
+class Extension;
+class ExtensionService;
+
+// For registering, loading, and unloading component extensions.
+class ComponentLoader {
+ public:
+  explicit ComponentLoader(ExtensionService* extension_service);
+  virtual ~ComponentLoader();
+
+  // Information about a registered component extension.
+  struct ComponentExtensionInfo {
+    ComponentExtensionInfo(const std::string& manifest,
+                           const FilePath& root_directory)
+        : manifest(manifest),
+          root_directory(root_directory) {
+    }
+
+    bool Equals(const ComponentExtensionInfo& other) const;
+
+    // The extension's manifest. This is required for component extensions so
+    // that ExtensionService doesn't need to go to disk to load them.
+    std::string manifest;
+
+    // Directory where the extension is stored.
+    FilePath root_directory;
+  };
+
+  // Loads any component extensions.
+  void LoadComponentExtensions();
+
+  // Loads particular component extension.
+  const Extension* LoadComponentExtension(const ComponentExtensionInfo& info);
+
+  // Unloads particular component extension.
+  void UnloadComponentExtension(const ComponentExtensionInfo& info);
+
+  // Register the component extensions.
+  //
+  // Component extension manifest must contain a 'key' property with a unique
+  // public key, serialized in base64. You can create a suitable value with the
+  // following commands on a unixy system:
+  //
+  //   ssh-keygen -t rsa -b 1024 -N '' -f /tmp/key.pem
+  //   openssl rsa -pubout -outform DER < /tmp/key.pem 2>/dev/null | base64 -w 0
+  void RegisterDefaultComponentExtensions();
+
+  // Registers an extension to be loaded as a component extension.
+  void RegisterComponentExtension(const ComponentExtensionInfo& info) {
+    component_extension_manifests_.push_back(info);
+  }
+
+  // Unregisters a component extension from the list of extensions to be loaded
+  void UnregisterComponentExtension(const ComponentExtensionInfo& info);
+
+  // List of registered component extensions (see Extension::Location).
+  typedef std::vector<ComponentExtensionInfo> RegisteredComponentExtensions;
+  RegisteredComponentExtensions component_extension_manifests_;
+
+ private:
+  ExtensionService* extension_service_;
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_COMPONENT_LOADER_H_