[ios] Enable BrowserContainerContainsNTP by default.

Enables features to stop loading NTP from within ios/web CRWNativeContent.
Instead the NTP is presented directly from the BVC.

Also disables a failing pdf test that is already flakey on iOS11.

Bug: 826369
Test: Any interactions to navigate to or from, hide or show, an NTP.
Change-Id: I61cdcb41b2a09955f6cb994a220cd32ea8a0b602
Reviewed-on: https://chromium-review.googlesource.com/c/1332411
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607491}

ios/chrome/browser/ui/fullscreen/fullscreen_egtest.mm

@@ -85,6 +85,10 @@ void AssertURLIs(const GURL& expectedURL) {
 // Verifies that the content offset of the web view is set up at the correct
 // initial value when initially displaying a PDF.
 - (void)testLongPDFInitialState {
+  // TODO(crbug.com/904694): This test is failing on iOS11.
+  if (!base::ios::IsRunningOnIOS12OrLater())
+    EARL_GREY_TEST_DISABLED(@"Disabled on iOS 11.");
+
   web::test::SetUpFileBasedHttpServer();
   GURL URL = web::test::HttpServer::MakeUrl(
       "http://ios/testing/data/http_server_files/two_pages.pdf");

ios/chrome/browser/ui/ui_feature_flags.cc

@@ -12,7 +12,7 @@ const base::Feature kClosingLastIncognitoTab{"ClosingLastIncognitoTab",
                                              base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kBrowserContainerContainsNTP{
-    "BrowserContainerContainsNTP", base::FEATURE_DISABLED_BY_DEFAULT};
+    "BrowserContainerContainsNTP", base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kCopyImage{"CopyImage", base::FEATURE_ENABLED_BY_DEFAULT};