Recreate the loader as soon as it is deleted and ensure that it does not become stale.

chrome/browser/instant/instant_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_INSTANT_INSTANT_CONTROLLER_H_
 #define CHROME_BROWSER_INSTANT_INSTANT_CONTROLLER_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string16.h"
 #include "base/timer.h"
 #include "chrome/browser/instant/instant_commit_type.h"
 #include "chrome/browser/instant/instant_loader_delegate.h"
 #include "chrome/common/instant_types.h"
 #include "content/public/common/page_transition_types.h"
 #include "googleurl/src/gurl.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/rect.h"
@@ skipping 114 matching lines @@
   virtual void SwappedTabContents(InstantLoader* loader) OVERRIDE;
   virtual void InstantLoaderContentsFocused(InstantLoader* loader) OVERRIDE;
 
 #if defined(UNIT_TEST)
   // Accessors used only in tests.
   bool is_showing() const { return is_showing_; }
   InstantLoader* loader() const { return loader_.get(); }
 #endif
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(InstantTest, InstantLoaderRefresh);
+
+  // Creates a new loader with the provided |instant_url| on the |active_tab|.
+  // Will also start the |loader_refresh_timer_|. The |loader_| should have been
+  // deleted before making this call.
+  void CreateLoader(const std::string& instant_url,
+                    const TabContents* active_tab);
+
   // Creates a new loader if necessary (for example, if the |instant_url| has
   // changed since the last time we created the loader).
   void ResetLoader(const std::string& instant_url,
                    const TabContents* active_tab);
 
+  // Ensures that the |loader_| uses the default instant url, recreating it if

[sreeram, 2012/08/22 17:39:35]

instant url -> Instant URL

[Shishir, 2012/08/23 18:26:33]

Done.

+  // necessary. Uses the current tab if the |loader_| needs to be recreated.

[sreeram, 2012/08/22 17:39:35]

You can lose this part ("Uses the current tab ... recreated"). It doesn't tell
much (why or how it is being used, or even why "current" tab, when in the next
line you call it "active" tab).

[Shishir, 2012/08/23 18:26:33]

Done.

+  // Will not do anything if the instant url could not be determined or the

[sreeram, 2012/08/22 17:39:35]

instant url -> Instant URL

[Shishir, 2012/08/23 18:26:33]

Done.

+  // active tab is NULL (browser is shutting down).
+  void ResetLoaderWithDefaultUrlAndCurrentTab();

[sreeram, 2012/08/22 17:39:35]

Rename this to CreateDefaultLoader().

[Shishir, 2012/08/23 18:26:33]

Done, but note that this need not create the loader if it already exists and has
the right url.

+
+  // Starts / restarts the |loader_refresh_timer_| to refresh interval from now.
+  void ScheduleLoaderRefresh();

[sreeram, 2012/08/22 17:39:35]

Rename to ResetStaleLoaderTimer?

[Shishir, 2012/08/23 18:26:33]

Done.

+
+  // If the |loader_| is not showing, it is deleted and recreated. Else the
+  // refresh is skipped and the next refresh is scheduled.
+  void RefreshLoader();

[sreeram, 2012/08/22 17:39:35]

Call this OnStaleLoader?

[Shishir, 2012/08/23 18:26:33]

Done.

+
   // Destroys the |loader_| and its preview contents.
   void DeleteLoader();
 
   // Counterpart to Hide(). Asks the |delegate_| to display the preview.
   void Show();
 
   // Send the omnibox dropdown bounds to the page.
   void SendBoundsToPage();
 
   // If |template_url| is a valid TemplateURL for use with Instant, fills in
@@ skipping 48 matching lines @@
 
   // Current omnibox bounds.
   gfx::Rect omnibox_bounds_;
 
   // Last bounds passed to the page.
   gfx::Rect last_omnibox_bounds_;
 
   // Timer used to update the bounds of the omnibox.
   base::OneShotTimer<InstantController> update_bounds_timer_;
 
+  // Timer used to ensure that the Instant page does not get too stale.
+  base::OneShotTimer<InstantController> loader_refresh_timer_;

[sreeram, 2012/08/22 17:39:35]

Call this stale_loader_timer_?

[Shishir, 2012/08/23 18:26:33]

Done.

+
   // For each key K => value N, the map says that we found that the search
   // engine identified by Instant URL K didn't support the Instant API in each
   // of the last N times that we loaded it. If an Instant URL isn't present in
   // the map at all or has a value 0, it means that search engine supports the
   // Instant API (or we assume it does, since we haven't determined it doesn't).
   std::map<std::string, int> blacklisted_urls_;
 
   // Search terms extraction (for autocomplete history matches) doesn't work
   // on Instant URLs. So, whenever the user commits an Instant search, we add
   // an equivalent non-Instant search URL to history, so that the search shows
   // up in autocomplete history matches.
   GURL url_for_history_;
 
   DISALLOW_COPY_AND_ASSIGN(InstantController);
 };
 
 #endif  // CHROME_BROWSER_INSTANT_INSTANT_CONTROLLER_H_