Attempt to deflake TrustedCdnPublisherTest.testOfflinePage

Opening multiple custom tabs in quick succession can lead to flakiness,
so load a new URL in the same tab instead.

Also use the correct icon for offline pages.

Bug: 833569
Change-Id: I87e83f65bd8883146398e5ddd9dfd7a7acd2a5c8
Reviewed-on: https://chromium-review.googlesource.com/1013923Reviewed-by: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Commit-Queue: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551352}

chrome/android/javatests/src/org/chromium/chrome/browser/customtabs/TrustedCdnPublisherUrlTest.java

@@ -355,10 +355,12 @@ public class TrustedCdnPublisherUrlTest {
         ThreadUtils.runOnUiThreadBlocking(
                 () -> { NetworkChangeNotifier.forceConnectivityState(false); });
 
-        // With no connectivity, loading the offline page should succeed,
-        // but not show a publisher URL.
-        runTrustedCdnPublisherUrlTest(
-                publisherUrl, "com.example.test", null, getDefaultSecurityIcon());
+        // Load the URL in the same tab. With no connectivity, loading the offline page should
+        // succeed, but not show a publisher URL.
+        String testUrl = mWebServer.getResponseUrl("/test.html");
+        mCustomTabActivityTestRule.loadUrl(testUrl);
+        verifyUrl(UrlFormatter.formatUrlForSecurityDisplay(testUrl, false));
+        verifySecurityIcon(R.drawable.offline_pin_round);
     }
 
     private void runTrustedCdnPublisherUrlTest(@Nullable String publisherUrl, String clientPackage,