add test for visibility detection

components/dom_distiller/content/distiller_page_web_contents_browsertest.cc

 // Copyright 2013 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.
 
 #include "base/memory/weak_ptr.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "base/values.h"
 #include "components/dom_distiller/content/distiller_page_web_contents.h"
 #include "components/dom_distiller/core/distiller_page.h"
@@ skipping 100 matching lines @@
   DistillPage(run_loop.QuitClosure(), "/simple_article.html");
   run_loop.Run();
 
   // A relative link should've been updated.
   EXPECT_THAT(page_info_.get()->html,
               ContainsRegex("src=\"http://127.0.0.1:.*/relativeimage.png\""));
   EXPECT_THAT(page_info_.get()->html,
               HasSubstr("src=\"http://www.google.com/absoluteimage.png\""));
 }
 
+IN_PROC_BROWSER_TEST_F(DistillerPageWebContentsTest, VisibilityDetection) {
+  DistillerPageWebContents distiller_page(
+      shell()->web_contents()->GetBrowserContext());
+  distiller_page_ = &distiller_page;
+
+  base::RunLoop run_loop;
+  DistillPage(run_loop.QuitClosure(), "/simple_article.html");
+  run_loop.Run();
+
+  EXPECT_THAT(page_info_.get()->html,
+              Not(HasSubstr("I am not supposed to appear")));

[cjhopman, 2014/05/14 16:59:52]

This test needs to ensure that when those elements aren't hidden they do appear
in the output (i.e. it needs to confirm that they aren't in the input in the
current case *because* they are hidden).

[kuan, 2014/05/14 18:57:24]

Done.  i'm not sure if this is what u meant.

+}
+
 }  // namespace dom_distiller