[ios] Don't rewrite the about NTP url twice.

Rewrite chrome://newtab to about://newtab, but don't rewrite
about://newtab twice.

Also adds unit tests.

Change-Id: I4744e84d0855c39b50076a9550aefe75812c4bf9
Reviewed-on: https://chromium-review.googlesource.com/c/1490959
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636183}

ios/chrome/browser/BUILD.gn

@@ -244,6 +244,7 @@ source_set("unit_tests") {
   testonly = true
   sources = [
     "app_startup_parameters_unittest.mm",
+    "browser_about_rewriter_unittest.cc",
     "chrome_browser_provider_observer_bridge_unittest.mm",
     "chrome_url_util_unittest.mm",
     "crash_loop_detection_util_unittest.mm",

ios/chrome/browser/browser_about_rewriter.cc

@@ -27,6 +27,8 @@ const struct HostReplacement {
 }  // namespace
 
 bool WillHandleWebBrowserAboutURL(GURL* url, web::BrowserState* browser_state) {
+  GURL original_url = *url;
+
   // Ensure that any cleanup done by FixupURL happens before the rewriting
   // phase that determines the virtual URL, by including it in an initial
   // URLHandler.  This prevents minor changes from producing a virtual URL,
@@ -48,7 +50,7 @@ bool WillHandleWebBrowserAboutURL(GURL* url, web::BrowserState* browser_state) {
       GURL::Replacements replacements;
       replacements.SetSchemeStr(url::kAboutScheme);
       *url = url->ReplaceComponents(replacements);
-      return true;
+      return *url != original_url;
     }
   }
 

ios/chrome/browser/browser_about_rewriter_unittest.cc

+// Copyright 2019 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 "ios/chrome/browser/browser_about_rewriter.h"
+
+#include "base/test/gtest_util.h"
+#include "ios/chrome/browser/chrome_url_constants.h"
+#include "testing/platform_test.h"
+#include "url/gurl.h"
+
+using BrowserAboutRewriterTest = PlatformTest;
+
+// Test that chrome://newtab is re-written to about://newtab,
+// but that about://newtab is not re-written twice.
+TEST_F(BrowserAboutRewriterTest, NtpTest) {
+  GURL url = GURL(kChromeUINewTabURL);
+  EXPECT_TRUE(WillHandleWebBrowserAboutURL(&url, /*browser_state=*/nullptr));
+  EXPECT_EQ(url, GURL(kChromeUIAboutNewTabURL));
+  EXPECT_FALSE(WillHandleWebBrowserAboutURL(&url, nil));
+}
+
+// Test that about|chrome://about is rewritten to chrome-urls.
+TEST_F(BrowserAboutRewriterTest, AboutTest) {
+  GURL url = GURL("about:about");
+  EXPECT_FALSE(WillHandleWebBrowserAboutURL(&url, /*browser_state=*/nullptr));
+  EXPECT_EQ(url, GURL("chrome://chrome-urls/"));
+
+  url = GURL("chrome://about/");
+  EXPECT_FALSE(WillHandleWebBrowserAboutURL(&url, /*browser_state=*/nullptr));
+  EXPECT_EQ(url, GURL("chrome://chrome-urls/"));
+}
+
+// Test that about|chrome://sync is rewritten to sync-internals.
+TEST_F(BrowserAboutRewriterTest, SyncTest) {
+  GURL url = GURL("about:sync");
+  EXPECT_FALSE(WillHandleWebBrowserAboutURL(&url, /*browser_state=*/nullptr));
+  EXPECT_EQ(url, GURL("chrome://sync-internals/"));
+
+  url = GURL("chrome://sync/");
+  EXPECT_FALSE(WillHandleWebBrowserAboutURL(&url, /*browser_state=*/nullptr));
+  EXPECT_EQ(url, GURL("chrome://sync-internals/"));
+}