[WebUI] Add a chrome://prefs-internals page

chrome/browser/ui/webui/prefs_internals_browsertest.cc

+// Copyright 2017 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 "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/test/browser_test_utils.h"
+#include "url/gurl.h"
+
+using PrefsInternalsTest = InProcessBrowserTest;
+
+IN_PROC_BROWSER_TEST_F(PrefsInternalsTest, TestSomethingIsServed) {
+  // First, check that navigation succeeds.
+  GURL kUrl("chrome://prefs-internals");
+  ui_test_utils::NavigateToURL(browser(), kUrl);
+  content::WebContents* web_contents =
+      browser()->tab_strip_model()->GetActiveWebContents();
+  ASSERT_TRUE(web_contents);
+  EXPECT_EQ(kUrl, web_contents->GetLastCommittedURL());
+  EXPECT_FALSE(web_contents->IsCrashed());
+  EXPECT_FALSE(web_contents->GetInterstitialPage());
+
+  // It's difficult to test the content of the page without duplicating the
+  // implementation, but we can at least assert that something is being shown.

[Dan Beam, 2017/03/08 18:40:58]

why not just set a string pref to a very unique value and check for that value?

[Devlin, 2017/03/20 19:25:31]

That's a good idea.  Done. (Very unique value == base::GenerateGUID())

+  bool has_text = false;
+  EXPECT_TRUE(content::ExecuteScriptAndExtractBool(
+      web_contents,
+      "window.domAutomationController.send("
+      "document.body.textContent && document.body.textContent.length > 0);",
+      &has_text));
+  EXPECT_TRUE(has_text);
+}