[iOS] Add Brave navigator JavaScriptFeature (#36021)

This adds a `JavaScriptFeature` based on the `BraveGetUA.js` to support `navigator.brave.isBrave` when the `UseProfileWebViewConfiguration` feature flag is enabled

ios/browser/web/BUILD.gn

@@ -34,6 +34,7 @@ source_set("web") {
     "//brave/ios/browser/web/document_fetch",
     "//brave/ios/browser/web/force_paste",
     "//brave/ios/browser/web/logins",
+    "//brave/ios/browser/web/navigator",
     "//brave/ios/browser/web/night_mode",
     "//brave/ios/browser/web/page_metadata",
     "//brave/ios/browser/web/reader_mode",

ios/browser/web/brave_web_client.mm

@@ -26,6 +26,7 @@
 #include "brave/ios/browser/web/document_fetch/document_fetch_javascript_feature.h"
 #include "brave/ios/browser/web/force_paste/force_paste_javascript_feature.h"
 #include "brave/ios/browser/web/logins/logins_javascript_feature.h"
+#include "brave/ios/browser/web/navigator/brave_navigator_javascript_feature.h"
 #include "brave/ios/browser/web/night_mode/night_mode_javascript_feature.h"
 #include "brave/ios/browser/web/page_metadata/page_metadata_javascript_feature.h"
 #include "brave/ios/browser/web/reader_mode/reader_mode_javascript_feature.h"
@@ -136,6 +137,7 @@ std::vector<web::JavaScriptFeature*> BraveWebClient::GetJavaScriptFeatures(
     features.push_back(
         brave_ads::AdsMediaReportingJavaScriptFeature::GetInstance());
     features.push_back(AIChatDistillerJavaScriptFeature::GetInstance());
+    features.push_back(BraveNavigatorJavaScriptFeature::GetInstance());
     features.push_back(BraveSearchAdResultsJavaScriptFeature::GetInstance());
 #if BUILDFLAG(ENABLE_BRAVE_TALK)
     features.push_back(BraveTalkLauncherJavaScriptFeature::GetInstance());

ios/browser/web/navigator/BUILD.gn

@@ -0,0 +1,24 @@
+# Copyright (c) 2026 The Brave Authors. All rights reserved.
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import("//ios/web/public/js_messaging/optimize_ts.gni")
+
+source_set("navigator") {
+  sources = [
+    "brave_navigator_javascript_feature.h",
+    "brave_navigator_javascript_feature.mm",
+  ]
+  deps = [ ":brave_navigator_js" ]
+  public_deps = [
+    "//base",
+    "//ios/web/public/js_messaging",
+  ]
+}
+
+optimize_ts("brave_navigator_js") {
+  visibility = [ ":navigator" ]
+
+  sources = [ "resources/brave_navigator.ts" ]
+}

ios/browser/web/navigator/brave_navigator_javascript_feature.h

@@ -0,0 +1,25 @@
+// Copyright (c) 2026 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#ifndef BRAVE_IOS_BROWSER_WEB_NAVIGATOR_BRAVE_NAVIGATOR_JAVASCRIPT_FEATURE_H_
+#define BRAVE_IOS_BROWSER_WEB_NAVIGATOR_BRAVE_NAVIGATOR_JAVASCRIPT_FEATURE_H_
+
+#include "base/no_destructor.h"
+#include "ios/web/public/js_messaging/java_script_feature.h"
+
+class BraveNavigatorJavaScriptFeature : public web::JavaScriptFeature {
+ public:
+  // This feature holds no state, so only a single static instance is ever
+  // needed.
+  static BraveNavigatorJavaScriptFeature* GetInstance();
+
+ private:
+  friend class base::NoDestructor<BraveNavigatorJavaScriptFeature>;
+
+  BraveNavigatorJavaScriptFeature();
+  ~BraveNavigatorJavaScriptFeature() override;
+};
+
+#endif  // BRAVE_IOS_BROWSER_WEB_NAVIGATOR_BRAVE_NAVIGATOR_JAVASCRIPT_FEATURE_H_

ios/browser/web/navigator/brave_navigator_javascript_feature.mm

@@ -0,0 +1,28 @@
+// Copyright (c) 2026 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#include "brave/ios/browser/web/navigator/brave_navigator_javascript_feature.h"
+
+namespace {
+constexpr char kScriptName[] = "brave_navigator";
+}  // namespace
+
+BraveNavigatorJavaScriptFeature::BraveNavigatorJavaScriptFeature()
+    : JavaScriptFeature(
+          web::ContentWorld::kPageContentWorld,
+          {FeatureScript::CreateWithFilename(
+              kScriptName,
+              FeatureScript::InjectionTime::kDocumentStart,
+              FeatureScript::TargetFrames::kAllFrames,
+              FeatureScript::ReinjectionBehavior::kInjectOncePerWindow)}) {}
+
+BraveNavigatorJavaScriptFeature::~BraveNavigatorJavaScriptFeature() = default;
+
+// static
+BraveNavigatorJavaScriptFeature*
+BraveNavigatorJavaScriptFeature::GetInstance() {
+  static base::NoDestructor<BraveNavigatorJavaScriptFeature> instance;
+  return instance.get();
+}

ios/browser/web/navigator/resources/brave_navigator.ts

@@ -0,0 +1,13 @@
+// Copyright (c) 2026 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+Object.defineProperty(navigator, 'brave', {
+  enumerable: false,
+  configurable: true,
+  writable: false,
+  value: Object.freeze({
+    isBrave: (): Promise<boolean> => Promise.resolve(true)
+  })
+});