re-use WebUIs

content/browser/web_contents/render_view_host_manager.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 CONTENT_BROWSER_WEB_CONTENTS_RENDER_VIEW_HOST_MANAGER_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_RENDER_VIEW_HOST_MANAGER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/logging.h"
@@ skipping 106 matching lines @@
   // there is no current one.
   content::RenderWidgetHostView* GetRenderWidgetHostView() const;
 
   // Returns the pending render view host, or NULL if there is no pending one.
   content::RenderViewHostImpl* pending_render_view_host() const;
 
   // Returns the current committed Web UI or NULL if none applies.
   WebUIImpl* web_ui() const { return web_ui_.get(); }
 
   // Returns the Web UI for the pending navigation, or NULL of none applies.
-  WebUIImpl* pending_web_ui() const { return pending_web_ui_.get(); }
+  WebUIImpl* pending_web_ui() const { return pending_web_ui_; }
 
   // Called when we want to instruct the renderer to navigate to the given
   // navigation entry. It may create a new RenderViewHost or re-use an existing
   // one. The RenderViewHost to navigate will be returned. Returns NULL if one
   // could not be created.
   content::RenderViewHostImpl* Navigate(
       const content::NavigationEntryImpl& entry);
 
   // Instructs the various live views to stop. Called when the user directed the
   // page to stop loading.
@@ skipping 74 matching lines @@
   // Returns true if the two navigation entries are incompatible in some way
   // other than site instances. Cases where this can happen include Web UI
   // to regular web pages. It will cause us to swap RenderViewHosts (and hence
   // RenderProcessHosts) even if the site instance would otherwise be the same.
   // As part of this, we'll also force new SiteInstances and BrowsingInstances.
   // Either of the entries may be NULL.
   bool ShouldSwapProcessesForNavigation(
       const content::NavigationEntry* cur_entry,
       const content::NavigationEntryImpl* new_entry) const;
 
+  bool ShouldReuseWebUI(
+      const content::NavigationEntry* curr_entry,

[Dan Beam, 2012/04/21 02:53:07]

can you change this to cur_entry or change above to curr_entry?

[Evan Stade, 2012/04/24 17:52:40]

Done.

+      const content::NavigationEntryImpl* new_entry) const;
+
   // Returns an appropriate SiteInstance object for the given NavigationEntry,
   // possibly reusing the current SiteInstance.
   // Never called if --process-per-tab is used.
   content::SiteInstance* GetSiteInstanceForEntry(
       const content::NavigationEntryImpl& entry,
       content::SiteInstance* curr_instance);
 
   // Helper method to create a pending RenderViewHost for a cross-site
   // navigation.
   bool CreatePendingRenderView(const content::NavigationEntryImpl& entry,
@@ skipping 12 matching lines @@
   // Helper method to terminate the pending RenderViewHost.
   void CancelPending();
 
   content::RenderViewHostImpl* UpdateRendererStateForNavigate(
       const content::NavigationEntryImpl& entry);
 
   // Called when a renderer process is starting to close.  We should not
   // schedule new navigations in its swapped out RenderViewHosts after this.
   void RendererProcessClosing(content::RenderProcessHost* render_process_host);
 
+  // Deletes |pending_web_ui_|, making sure not to double-free in the case where
+  // it is the same as |web_ui_|.
+  void FreePendingWebUI();
+
   // Our delegate, not owned by us. Guaranteed non-NULL.
   Delegate* delegate_;
 
   // Whether a navigation requiring different RenderView's is pending. This is
   // either cross-site request is (in the new process model), or when required
   // for the view type (like view source versus not).
   bool cross_navigation_pending_;
 
   // Implemented by the owner of this class, this delegate is installed into all
   // the RenderViewHosts that we create.
   content::RenderViewHostDelegate* render_view_delegate_;
 
   // Our RenderView host and its associated Web UI (if any, will be NULL for
   // non-DOM-UI pages). This object is responsible for all communication with
   // a child RenderView instance.
   content::RenderViewHostImpl* render_view_host_;
   scoped_ptr<WebUIImpl> web_ui_;
 
   // A RenderViewHost used to load a cross-site page. This remains hidden
   // while a cross-site request is pending until it calls DidNavigate. It may
   // have an associated Web UI, in which case the Web UI pointer will be non-
   // NULL.
   //
-  // The pending_web_ui may be non-NULL even when the pending_render_view_host_
+  // The pending_web_ui_ may be non-NULL even when the pending_render_view_host_

[Dan Beam, 2012/04/21 02:53:07]

nit: |pending_web_ui_| and |pending_render_view_host_| if you want to

[Evan Stade, 2012/04/24 17:52:40]

Done.

   // is. This will happen when we're transitioning between two Web UI pages:
   // the RVH won't be swapped, so the pending pointer will be unused, but there
   // will be a pending Web UI associated with the navigation.
   content::RenderViewHostImpl* pending_render_view_host_;
-  scoped_ptr<WebUIImpl> pending_web_ui_;
+
+  // If non-NULL, the pending navigation is to a chrome: page. The pointer may
+  // be a unique WebUIImpl, or may be a copy of web_ui_, in which case the same
+  // WebUIImpl* will be reused for the next navigation.
+  WebUIImpl* pending_web_ui_;

[stuartmorgan, 2012/04/24 09:12:20]

This memory model makes me *extremely* nervous; I think it's almost certain that
someone will introduce a leak or a crash eventually this way (doubly so since
this class is both very complex and weakly owned).

I can see two sane approaches here:
1) A trivial ref-counted class that wraps WebUIImpl*, so that you can use that
as the type for two scoped_refptrs, or
2) A little helper class that owns both WebUIImpl objects and has a handful of
public methods that do what you need (checks if there is a pending web ui,
returns the pending web ui, commits the pending web ui).

[Evan Stade, 2012/04/24 17:52:40]

Done.

 
   // A map of site instance ID to swapped out RenderViewHosts.
   typedef base::hash_map<int32, content::RenderViewHostImpl*> RenderViewHostMap;
   RenderViewHostMap swapped_out_hosts_;
 
   // The intersitial page currently shown if any, not own by this class
   // (the InterstitialPage is self-owned, it deletes itself when hidden).
   InterstitialPageImpl* interstitial_page_;
 
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewHostManager);
 };
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_RENDER_VIEW_HOST_MANAGER_H_