Implement <webview>.addContentScript/removeContentScript API [2]

extensions/browser/guest_view/web_view/web_ui/web_ui_url_fetcher_group.h

+// Copyright 2015 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 EXTENSIONS_BROWSER_WEB_UI_URL_FETCHER_GROUP_H
+#define EXTENSIONS_BROWSER_WEB_UI_URL_FETCHER_GROUP_H
+
+#include <set>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_vector.h"
+#include "extensions/browser/guest_view/web_view/web_ui/web_ui_url_fetcher.h"
+#include "extensions/common/user_script.h"
+
+namespace content {
+class BrowserContext;
+}
+
+// WebUIURLFetcherGroup receives a set of user script file load tasks, and
+// starts a group of async URL fetchs. When all the fetches are done, it runs
+// the callback from the owner of the group.
+class WebUIURLFetcherGroup : public base::RefCounted<WebUIURLFetcherGroup> {

[Devlin, 2015/04/16 20:19:28]

Can you think of a way this could avoid being refcounted?

[Xi Han, 2015/04/17 21:44:20]

It needs to be RefCounted since in web_ui_url_fetcher_group.cc (line 26) we can
bind WebUIURLFtcherGroup::OnWebUIURLFetchComplete() and a pointer of
WebUIURLFtcherGroup as the call back to create a new WebUIURLFetcher. 

[Devlin, 2015/04/17 22:05:05]

The callback will be called by the WebUIURLFetcher, which is owned by this
class.  If the WebUIURLFetcherGroup is destroyed, the WebUIURLFetcher is
destroyed, and there is nothing to call the callback.  Right?

[Xi Han, 2015/04/17 22:28:24]

I am confused. I assume the WebUIURLFetcherGroup will be destroyed only when the
all of the callbacks are called. Right?

[Devlin, 2015/04/17 22:40:15]

If you recount it, yes, it will only be destroyed once all references have been
destroyed, including those references in the callbacks.  So if the callbacks are
the last thing there, then yes, it will be destroyed after they all run.  If you
do *not* refcount it, it will be destroyed in the "normal" fashion (being
deleted, going out of scope, etc).  Without refcounting, binding an object does
not extend its lifetime.

[Xi Han, 2015/04/20 22:40:10]

Removed.

+ public:
+  WebUIURLFetcherGroup(content::BrowserContext* context,
+                       const base::Closure& callback);
+
+  // Starts URL requests to load the contents of several files from the
+  // associated render specified by |render_process_id, render_view_id|.
+  void Start(std::set<extensions::UserScript::File*> file_set,
+             int render_process_id,
+             int render_view_id);
+
+ private:
+  friend class base::RefCounted<WebUIURLFetcherGroup>;
+
+  virtual ~WebUIURLFetcherGroup();
+
+  // Called when each single URL fetch is complete. It also traces the number of
+  // complete fetches. If all the fetches are done, runs the callback function
+  // from the owner of this group.
+  void OnWebUIURLFetchComplete(extensions::UserScript::File* script_file,
+                               bool success,
+                               const std::string& data);
+
+  content::BrowserContext* context_;
+
+  // The number of complete fetchs.
+  size_t complete_fetchers_;
+
+  ScopedVector<WebUIURLFetcher> fetchers_;

[Devlin, 2015/04/16 20:19:28]

Since WebUIURLFetcher is pretty much just a tiny wrapper around URLFetcher,
would it be possible to instead make WebUIURLFetcher support multiple requests,
and get rid of this class?

[Xi Han, 2015/04/17 21:44:20]

As discussed offline, I still adopt the way to keep this group to organize a
group of fetches.

+  base::Closure callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebUIURLFetcherGroup);
+};
+
+#endif  // EXTENSIONS_BROWSER_WEB_UI_URL_FETCHER_GROUP_H