Fixes bug in instant that resulted in flickery fade. The problem would

chrome/browser/instant/instant_controller.h

 // Copyright (c) 2010 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_
 #pragma once
 
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/scoped_ptr.h"
 #include "base/scoped_vector.h"
 #include "base/string16.h"
 #include "base/task.h"
 #include "base/timer.h"
 #include "chrome/browser/instant/instant_commit_type.h"
 #include "chrome/browser/instant/instant_loader_delegate.h"
 #include "chrome/browser/search_engines/template_url_id.h"
 #include "chrome/common/page_transition_types.h"
 #include "gfx/native_widget_types.h"
 #include "gfx/rect.h"
 #include "googleurl/src/gurl.h"
 
 struct AutocompleteMatch;
 class InstantDelegate;
 class InstantLoader;
 class InstantLoaderManager;
+class InstantTest;
 class PrefService;
 class Profile;
 class TabContents;
 class TabContentsWrapper;
 class TemplateURL;
 
 // InstantController maintains a TabContents that is intended to give a preview
 // of a URL. InstantController is owned by Browser.
 //
 // At any time the TabContents maintained by InstantController may be destroyed
@@ skipping 106 matching lines @@
   // Does cleanup after the preview contents has been added to the tabstrip.
   // Invoke this if you explicitly invoke ReleasePreviewContents.
   void CompleteRelease(TabContents* tab);
 
   // TabContents the match is being shown for.
   TabContentsWrapper* tab_contents() const { return tab_contents_; }
 
   // The preview TabContents; may be null.
   TabContentsWrapper* GetPreviewContents();
 
-  // Returns true if the preview TabContents is active. In some situations this
-  // may return false yet preview_contents() returns non-NULL.
+  // Returns true if |Update| has been invoked without a corresponding call to
+  // |DestroyPreviewContents| or |CommitCurrentPreview|.
   bool is_active() const { return is_active_; }
 
+  // Returns true if the preview TabContents is ready to be displayed. In some
+  // situations this may return false yet GetPreviewContents() returns non-NULL.
+  bool is_displayable() const { return is_displayable_; }
+
   // Returns the transition type of the last AutocompleteMatch passed to Update.
   PageTransition::Type last_transition_type() const {
     return last_transition_type_;
   }
 
   // Returns true if we're showing results from a provider that supports the
   // instant API. See description of |MightSupportInstant| for how this
   // differs from actual loading state.
   bool IsShowingInstant();
 
@@ skipping 14 matching lines @@
   virtual void SetSuggestedTextFor(InstantLoader* loader,
                                    const string16& text);
   virtual gfx::Rect GetInstantBounds();
   virtual bool ShouldCommitInstantOnMouseUp();
   virtual void CommitInstantLoader(InstantLoader* loader);
   virtual void InstantLoaderDoesntSupportInstant(InstantLoader* loader);
   virtual void AddToBlacklist(InstantLoader* loader, const GURL& url);
 
 
  private:
+  friend class InstantTest;
+
   typedef std::set<std::string> HostBlacklist;
 
+  // Destroys the current loaders but remains actives.
+  void DestroyAndLeaveActive();
+
+  // Returns the TabContents of the pending loader (or NULL). This is only used
+  // for testing.
+  TabContentsWrapper* GetPendingPreviewContents();
+
   // Returns true if we should update immediately.
   bool ShouldUpdateNow(TemplateURLID instant_id, const GURL& url);
 
   // Schedules a delayed update to load the specified url.
   void ScheduleUpdate(const GURL& url);
 
   // Invoked from the timer to process the last scheduled url.
   void ProcessScheduledUpdate();
 
   // Updates InstantLoaderManager and its current InstantLoader. This is invoked
@@ skipping 40 matching lines @@
 
   // Returns a string description for the currently enabled type. This is used
   // for histograms.
   static std::string GetTypeString(Profile* profile);
 
   InstantDelegate* delegate_;
 
   // The TabContents last passed to |Update|.
   TabContentsWrapper* tab_contents_;
 
+  // See description above getter for details.
+  bool is_active_;
+
   // Has notification been sent out that the preview TabContents is ready to be
   // shown?
-  bool is_active_;
+  bool is_displayable_;
 
   // See description above setter.
   gfx::Rect omnibox_bounds_;
 
   // See description above CommitOnMouseUp.
   bool commit_on_mouse_up_;
 
   // See description above getter.
   PageTransition::Type last_transition_type_;
 
@@ skipping 19 matching lines @@
   ScopedVector<InstantLoader> loaders_to_destroy_;
 
   // The set of hosts that we don't use instant with. This is shared across all
   // instances and only maintained for the current session.
   static HostBlacklist* host_blacklist_;
 
   DISALLOW_COPY_AND_ASSIGN(InstantController);
 };
 
 #endif  // CHROME_BROWSER_INSTANT_INSTANT_CONTROLLER_H_