Change visibility semantics for Instant.

chrome/browser/ui/cocoa/tab_contents/previewable_contents_controller.mm

 // Copyright (c) 2011 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.
 
 #import "chrome/browser/ui/cocoa/tab_contents/previewable_contents_controller.h"
 
 #include "base/logging.h"
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 15 matching lines @@
   DCHECK(preview);
 
   // Remove any old preview contents before showing the new one.
   if (previewContents_)
     [previewContents_->GetNativeView() removeFromSuperview];
 
   previewContents_ = preview;
   NSView* previewView = previewContents_->GetNativeView();
   [previewView setFrame:[[self view] bounds]];
 
-  // Hide the active container and add the preview contents.
-  [activeContainer_ setHidden:YES];
+  // Add the preview contents.
   [[self view] addSubview:previewView];
+  previewContents_->WasShown();
 }
 
 - (void)hidePreview {
   // There may be no previewContents_ in the prerender case.
   if (!previewContents_)
     return;
 
-  // Remove the preview contents and reshow the active container.
+  // Remove the preview contents.
   [previewContents_->GetNativeView() removeFromSuperview];
-  [activeContainer_ setHidden:NO];
-
+  previewContents_->WasHidden();
   previewContents_ = nil;
 }
 
 - (BOOL)isShowingPreview {
   return previewContents_ != nil;
 }
 
 @end