Quickly close tabs/window with long-running unload handlers.

chrome/browser/ui/unload_controller.h

 // Copyright (c) 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_UI_UNLOAD_CONTROLLER_H_
 #define CHROME_BROWSER_UI_UNLOAD_CONTROLLER_H_
 
 #include <set>
 
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/strings/string_piece.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 class Browser;
 class TabStripModel;
 
 namespace content {
 class NotificationSource;
 class NotifictaionDetails;
 class WebContents;
 }
 
 namespace chrome {
-
+// UnloadController manages closing tabs and windows -- especially in
+// regards to beforeunload handlers (have proceed/cancel dialogs) and
+// unload handlers (have no user interaction).
+//
+// Typical flow of closing a tab:
+//  1. Browser calls CanCloseContents().
+//     If true, browser calls contents::CloseWebContents().
+//  2. WebContents notifies us via its delegate and BeforeUnloadFired()
+//     that the beforeunload handler was run. If the user allowed the
+//     close to continue, we detached the tab and hold onto it while the
+//     close finishes.
+//
+// Typical flow of closing a window:
+//  1. BrowserView::CanClose() calls TabsNeedBeforeUnloadFired().
+//     If beforeunload/unload handlers need to run, UnloadController returns
+//     true and calls ProcessPendingTabs() (private method).
+//  2. For each tab with a beforeunload/unload handler, ProcessPendingTabs()
+//        calls |web_contents->OnCloseStarted()|
+//        and   |web_contents->GetRenderViewHost()->FirePageBeforeUnload()|.
+//  3. If the user allowed the close to continue, we detach all the tabs with
+//     unload handlers, remove them from the tab strip, and finish closing
+//     the tabs in the background.
+//  4. The browser gets notified that the tab strip is empty and calls
+//     CloseFrame where the empty tab strip causes the window to hide.
+//     Once the detached tabs finish, the browser calls CloseFrame again and
+//     the window is finally closed.
+//
 class UnloadController : public content::NotificationObserver,
                          public TabStripModelObserver {
  public:
   explicit UnloadController(Browser* browser);
   virtual ~UnloadController();
 
   // Returns true if |contents| can be cleanly closed. When |browser_| is being
   // closed, this function will return false to indicate |contents| should not
   // be cleanly closed, since the fast shutdown path will just kill its
   // renderer.
   bool CanCloseContents(content::WebContents* contents);
 
   // Called when a BeforeUnload handler is fired for |contents|. |proceed|
   // indicates the user's response to the Y/N BeforeUnload handler dialog. If
   // this parameter is false, any pending attempt to close the whole browser
   // will be canceled. Returns true if Unload handlers should be fired. When the
   // |browser_| is being closed, Unload handlers for any particular WebContents
   // will not be run until every WebContents being closed has a chance to run
   // its BeforeUnloadHandler.
   bool BeforeUnloadFired(content::WebContents* contents, bool proceed);
 
   bool is_attempting_to_close_browser() const {
     return is_attempting_to_close_browser_;
   }
 
   // Called in response to a request to close |browser_|'s window. Returns true
-  // when there are no remaining unload handlers to be run.
+  // when there are no remaining beforeunload handlers to be run.
   bool ShouldCloseWindow();
 
   // Returns true if |browser_| has any tabs that have BeforeUnload handlers
   // that have not been fired. This method is non-const because it builds a list
   // of tabs that need their BeforeUnloadHandlers fired.
   // TODO(beng): This seems like it could be private but it is used by
   //             AreAllBrowsersCloseable() in application_lifetime.cc. It seems
   //             very similar to ShouldCloseWindow() and some consolidation
   //             could be pursued.
   bool TabsNeedBeforeUnloadFired();
 
+  // Returns true if all tabs' beforeunload/unload events have fired.
+  bool HasCompletedUnloadProcessing() const;
+
  private:
-  typedef std::set<content::WebContents*> UnloadListenerSet;
-
   // Overridden from content::NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
   // Overridden from TabStripModelObserver:
   virtual void TabInsertedAt(content::WebContents* contents,
                              int index,
                              bool foreground) OVERRIDE;
   virtual void TabDetachedAt(content::WebContents* contents,
                              int index) OVERRIDE;
   virtual void TabReplacedAt(TabStripModel* tab_strip_model,
                              content::WebContents* old_contents,
                              content::WebContents* new_contents,
                              int index) OVERRIDE;
   virtual void TabStripEmpty() OVERRIDE;
 
   void TabAttachedImpl(content::WebContents* contents);
   void TabDetachedImpl(content::WebContents* contents);
 
+  // Detach |contents| and wait for it to finish closing.
+  // The close must be inititiated outside of this method.

[Avi (use Gerrit), 2013/06/10 03:32:40]

typo: inititiated

+  // Returns true if it succeeds.
+  bool DetachWebContents(content::WebContents* contents);
+
   // Processes the next tab that needs it's beforeunload/unload event fired.
   void ProcessPendingTabs();
 
-  // Whether we've completed firing all the tabs' beforeunload/unload events.
-  bool HasCompletedUnloadProcessing() const;
-
   // Clears all the state associated with processing tabs' beforeunload/unload
   // events since the user cancelled closing the window.
   void CancelWindowClose();
 
-  // Removes |web_contents| from the passed |set|.
-  // Returns whether the tab was in the set in the first place.
-  bool RemoveFromSet(UnloadListenerSet* set,
-                     content::WebContents* web_contents);
+  // Cleans up state appropriately when we are trying to close the
+  // browser or close a tab in the background. We also use this in the
+  // cases where a tab crashes or hangs even if the
+  // beforeunload/unload haven't successfully fired.
+  void ClearUnloadState(content::WebContents* contents);
 
-  // Cleans up state appropriately when we are trying to close the browser and
-  // the tab has finished firing its unload handler. We also use this in the
-  // cases where a tab crashes or hangs even if the beforeunload/unload haven't
-  // successfully fired. If |process_now| is true |ProcessPendingTabs| is
-  // invoked immediately, otherwise it is invoked after a delay (PostTask).
-  //
-  // Typically you'll want to pass in true for |process_now|. Passing in true
-  // may result in deleting |tab|. If you know that shouldn't happen (because of
-  // the state of the stack), pass in false.
-  void ClearUnloadState(content::WebContents* web_contents, bool process_now);
+  // Helper for |ClearUnloadState| to unwind stack before proceeding.
+  void PostTaskForProcessPendingTabs();
+
+  // Log a step of the unload processing.
+  void LogUnloadStep(const base::StringPiece& step_name,
+                     content::WebContents* contents) const;
 
   Browser* browser_;
 
   content::NotificationRegistrar registrar_;
 
-  // Tracks tabs that need there beforeunload event fired before we can
-  // close the browser. Only gets populated when we try to close the browser.
-  UnloadListenerSet tabs_needing_before_unload_fired_;
+  typedef std::set<content::WebContents*> WebContentsSet;
 
-  // Tracks tabs that need there unload event fired before we can
-  // close the browser. Only gets populated when we try to close the browser.
-  UnloadListenerSet tabs_needing_unload_fired_;
+  // Tracks tabs that need their beforeunload event started.
+  // Only gets populated when we try to close the browser.
+  WebContentsSet tabs_needing_before_unload_;
+
+  // Tracks the tab that needs its beforeunload event result.
+  // Only gets populated when we try to close the browser.
+  content::WebContents* tab_needing_before_unload_ack_;
+
+  // Tracks tabs that need their unload event started.
+  // Only gets populated when we try to close the browser.
+  WebContentsSet tabs_needing_unload_;
+
+  // Tracks tabs that need to finish running their unload event.
+  // Populated both when closing individual tabs and when closing the browser.
+  WebContentsSet tabs_needing_unload_ack_;
 
   // Whether we are processing the beforeunload and unload events of each tab
   // in preparation for closing the browser. UnloadController owns this state
   // rather than Browser because unload handlers are the only reason that a
   // Browser window isn't just immediately closed.
   bool is_attempting_to_close_browser_;
 
+  // Manage tabs with beforeunload/unload handlers that close detached.
+  class DetachedWebContentsDelegate;
+  scoped_ptr<DetachedWebContentsDelegate> detached_delegate_;
+
   base::WeakPtrFactory<UnloadController> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UnloadController);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_UNLOAD_CONTROLLER_H_