Alternate NTP: Fix bug where shadow is not removed

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

 // Copyright 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.
 
 #import "chrome/browser/ui/cocoa/tab_contents/previewable_contents_controller.h"
 
 #include "chrome/browser/instant/instant_model.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_window.h"
@@ skipping 111 matching lines @@
   EXPECT_TRUE([controller_ dropShadowView]);
   EXPECT_TRUE([controller_ drawDropShadow]);
   EXPECT_NSEQ([controller_ view], [[controller_ dropShadowView] superview]);
 
   NSRect dropShadowFrame = [[controller_ dropShadowView] frame];
   NSRect controllerBounds = [[controller_ view] bounds];
   EXPECT_EQ(NSWidth(controllerBounds), NSWidth(dropShadowFrame));
   EXPECT_EQ([PreviewDropShadowView preferredHeight],
             NSHeight(dropShadowFrame));
 }
+
+// Verify that the shadow is hidden when hiding the preview.
+IN_PROC_BROWSER_TEST_F(PreviewableContentsControllerTest, HideShadow) {
+  chrome::search::Mode mode;
+  mode.mode = chrome::search::Mode::MODE_SEARCH_SUGGESTIONS;
+  instant_model_.SetPreviewState(mode, 10, INSTANT_SIZE_PERCENT);
+  EXPECT_TRUE([controller_ dropShadowView]);
+
+  [controller_ onActivateTabWithContents:web_contents_.get()];
+  EXPECT_FALSE([controller_ dropShadowView]);
+}