add test for visibility detection

components/dom_distiller/content/distiller_page_web_contents_browsertest.cc

Index: components/dom_distiller/content/distiller_page_web_contents_browsertest.cc
diff --git a/components/dom_distiller/content/distiller_page_web_contents_browsertest.cc b/components/dom_distiller/content/distiller_page_web_contents_browsertest.cc
index 3d20a9d9137e2ddd089d008006a8f12862a0a3d9..5e0d8946c84f6b1b4f40f0a8ba5541740d3a7e58 100644
--- a/components/dom_distiller/content/distiller_page_web_contents_browsertest.cc
+++ b/components/dom_distiller/content/distiller_page_web_contents_browsertest.cc
@@ -118,4 +118,17 @@ IN_PROC_BROWSER_TEST_F(DistillerPageWebContentsTest, HandlesRelativeImages) {
               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