[iOS] Add a feature flag for Safe Browsing

This adds a feature flag for Safe Browsing, and disables WKWebView's version
of Safe Browsing when this flag is enabled.

Bug: 1028755, 1050174
Change-Id: I213a3fb1aeaeaa4b497e7ba56be2c61046a5b688
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2065550Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Ali Juma <ajuma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743085}

ios/web/common/features.h

@@ -55,6 +55,11 @@ extern const base::Feature kUseDefaultUserAgentInWebClient;
 // of properties using hard coded logic.
 extern const base::Feature kPreserveScrollViewProperties;
 
+// Feature flag for making native (instead of WKWebView-provided) Safe
+// Browsing available. When this flag is enabled, Safe Browsing is still
+// subject to an opt-out controlled by prefs::kSafeBrowsingEnabled.
+extern const base::Feature kSafeBrowsingAvailable;
+
 // Use WKWebView.loading to update WebState::IsLoading.
 // TODO(crbug.com/1006012): Clean up this flag after experiment.
 bool UseWKWebViewLoading();

ios/web/common/features.mm

@@ -47,6 +47,9 @@ const base::Feature kUseDefaultUserAgentInWebClient{
 const base::Feature kPreserveScrollViewProperties{
     "PreserveScrollViewProperties", base::FEATURE_DISABLED_BY_DEFAULT};
 
+const base::Feature kSafeBrowsingAvailable{"SafeBrowsingAvailable",
+                                           base::FEATURE_DISABLED_BY_DEFAULT};
+
 bool UseWKWebViewLoading() {
   return base::FeatureList::IsEnabled(web::features::kUseWKWebViewLoading);
 }

ios/web/web_state/ui/wk_web_view_configuration_provider.mm

@@ -130,6 +130,14 @@ void WKWebViewConfigurationProvider::ResetWithWebViewConfiguration(
     } @catch (NSException* exception) {
       NOTREACHED() << "Error setting value for longPressActionsEnabled";
     }
+
+    // WKWebView's "fradulentWebsiteWarning" is an iOS 13+ feature that is
+    // conceptually similar to Safe Browsing but uses a non-Google provider and
+    // only works for devices in certain locales. Disable this feature when
+    // Safe Browsing is available.
+    if (base::FeatureList::IsEnabled(web::features::kSafeBrowsingAvailable)) {
+      [[configuration_ preferences] setFraudulentWebsiteWarningEnabled:NO];
+    }
   }
 
   [configuration_ setAllowsInlineMediaPlayback:YES];