[SH iOS] Adding hooks for Text Fragments during navigation

This CL adds a new file, text_fragment_utils, which will provide logic
for handling text fragments (the URL specifiers which power the
scroll-to-text feature). It invokes those utils at the last possible
moment of navigation.

I've implemented the basic guard logic that checks the preconditions
for completing such a navigation; actually performing the scroll to text
will be added in a follow-up CL.

Bug: 1099268

Change-Id: I522119abe28cc0bd323bdf230a1ca8951c157835
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2333044Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Tommy Martino <tmartino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794687}

ios/web/BUILD.gn

@@ -271,6 +271,7 @@ source_set("ios_web_navigation_unittests") {
     "navigation/navigation_manager_util_unittest.mm",
     "navigation/nscoder_util_unittest.mm",
     "navigation/session_storage_builder_unittest.mm",
+    "navigation/text_fragment_utils_unittest.mm",
     "navigation/wk_back_forward_list_item_holder_unittest.mm",
     "navigation/wk_based_navigation_manager_impl_unittest.mm",
     "navigation/wk_navigation_action_policy_util_unittest.mm",

ios/web/navigation/BUILD.gn

@@ -61,6 +61,8 @@ source_set("navigation") {
     "serializable_user_data_manager_impl.mm",
     "session_storage_builder.h",
     "session_storage_builder.mm",
+    "text_fragment_utils.h",
+    "text_fragment_utils.mm",
     "time_smoother.cc",
     "time_smoother.h",
     "url_schemes.mm",

ios/web/navigation/text_fragment_utils.h

+// Copyright 2020 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.
+
+#ifndef IOS_WEB_NAVIGATION_TEXT_FRAGMENT_UTILS_H_
+#define IOS_WEB_NAVIGATION_TEXT_FRAGMENT_UTILS_H_
+
+namespace web {
+
+class NavigationContext;
+
+// This file contains helper functions relating to Text Fragments, which are
+// appended to the reference fragment in the URL and instruct the user agent
+// to highlight a given snippet of text and the page and scroll it into view.
+// See also: https://wicg.github.io/scroll-to-text-fragment/
+
+// Checks if product and security requirements permit the use of Text Fragments.
+// Does not guarantee that the URL contains a Text Fragment or that the matching
+// text will be found on the page.
+bool AreTextFragmentsAllowed(NavigationContext* context);
+
+// Checks the destination URL for Text Fragments. If found, searches the DOM for
+// matching text, highlights the text, and scrolls the first into view.
+void HandleTextFragments(NavigationContext* context);
+
+}  // namespace web
+
+#endif  // IOS_WEB_NAVIGATION_TEXT_FRAGMENT_UTILS_H_

ios/web/navigation/text_fragment_utils.mm

+// Copyright 2020 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.
+
+#import "ios/web/navigation/text_fragment_utils.h"
+
+#include "ios/web/common/features.h"
+#import "ios/web/public/navigation/navigation_context.h"
+#import "ios/web/public/web_state.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace web {
+
+bool AreTextFragmentsAllowed(NavigationContext* context) {
+  if (!base::FeatureList::IsEnabled(features::kScrollToTextIOS))
+    return false;
+
+  WebState* web_state = context->GetWebState();
+  if (web_state->HasOpener()) {
+    // TODO(crbug.com/1099268): Loosen this restriction if the opener has the
+    // same domain.
+    return false;
+  }
+
+  return context->HasUserGesture() && !context->IsSameDocument();
+}
+
+void HandleTextFragments(NavigationContext* context) {
+  // TODO(crbug.com/1099268): Parse URL fragment, execute JS using passed
+  // params.
+}
+
+}  // namespace web

ios/web/navigation/text_fragment_utils_unittest.mm

+// Copyright 2020 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.
+
+#import "ios/web/navigation/text_fragment_utils.h"
+
+#include <memory>
+
+#include "base/test/scoped_feature_list.h"
+#include "ios/web/common/features.h"
+#import "ios/web/public/test/fakes/fake_navigation_context.h"
+#import "ios/web/public/test/fakes/test_web_state.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/platform_test.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace web {
+
+typedef PlatformTest TextFragmentUtilsTest;
+
+TEST_F(TextFragmentUtilsTest, AreTextFragmentsAllowed) {
+  base::test::ScopedFeatureList feature_list;
+  feature_list.InitAndEnableFeature(features::kScrollToTextIOS);
+
+  std::unique_ptr<TestWebState> web_state = std::make_unique<TestWebState>();
+  TestWebState* web_state_ptr = web_state.get();
+  FakeNavigationContext context;
+  context.SetWebState(std::move(web_state));
+
+  // Working case: no opener, has user gesture, not same document
+  web_state_ptr->SetHasOpener(false);
+  context.SetHasUserGesture(true);
+  context.SetIsSameDocument(false);
+  EXPECT_TRUE(AreTextFragmentsAllowed(&context));
+
+  // Blocking case #1: WebState has an opener
+  web_state_ptr->SetHasOpener(true);
+  context.SetHasUserGesture(true);
+  context.SetIsSameDocument(false);
+  EXPECT_FALSE(AreTextFragmentsAllowed(&context));
+
+  // Blocking case #2: No user gesture
+  web_state_ptr->SetHasOpener(false);
+  context.SetHasUserGesture(false);
+  context.SetIsSameDocument(false);
+  EXPECT_FALSE(AreTextFragmentsAllowed(&context));
+
+  // Blocking case #3: Same-document navigation
+  web_state_ptr->SetHasOpener(false);
+  context.SetHasUserGesture(true);
+  context.SetIsSameDocument(true);
+  EXPECT_FALSE(AreTextFragmentsAllowed(&context));
+}
+
+}  // namespace web

ios/web/web_state/web_state_impl.mm

@@ -20,6 +20,7 @@
 #import "ios/web/navigation/navigation_context_impl.h"
 #import "ios/web/navigation/navigation_item_impl.h"
 #import "ios/web/navigation/session_storage_builder.h"
+#import "ios/web/navigation/text_fragment_utils.h"
 #import "ios/web/navigation/wk_based_navigation_manager_impl.h"
 #import "ios/web/navigation/wk_navigation_util.h"
 #include "ios/web/public/browser_state.h"
@@ -858,6 +859,10 @@ void WebStateImpl::OnNavigationFinished(web::NavigationContextImpl* context) {
       observer.FaviconUrlUpdated(this, cached_favicon_urls_);
     }
   }
+
+  if (AreTextFragmentsAllowed(context)) {
+    HandleTextFragments(context);
+  }
 }
 
 #pragma mark - NavigationManagerDelegate implementation