Fix IsBraveAdsNotificationChannelEnabled().

In browser-android-tabs, we were adding a new method GetChannelStatus directly
in chromium's NotificationChannelsProviderAndroid class. To avoid patching,
this commit add BraveNotificationSettingsBridge for our native code to get
Ads channel status without patching chromium.

android/brave_java_sources.gni

@@ -26,6 +26,7 @@ brave_java_sources = [
   "../../brave/android/java/org/chromium/chrome/browser/document/BraveLauncherActivity.java",
   "../../brave/android/java/org/chromium/chrome/browser/notifications/BraveAds.java",
   "../../brave/android/java/org/chromium/chrome/browser/notifications/BraveAdsNotificationBuilder.java",
+  "../../brave/android/java/org/chromium/chrome/browser/notifications/BraveNotificationSettingsBridge.java",
   "../../brave/android/java/org/chromium/chrome/browser/notifications/BraveOnboardingNotification.java",
   "../../brave/android/java/org/chromium/chrome/browser/notifications/BraveSetDefaultBrowserNotificationService.java",
   "../../brave/android/java/org/chromium/chrome/browser/ntp/BraveDuckDuckGoOfferView.java",

android/java/org/chromium/chrome/browser/notifications/BraveNotificationSettingsBridge.java

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) 2019 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 http://mozilla.org/MPL/2.0/.
+ */
+
+package org.chromium.chrome.browser.notifications;
+
+import android.annotation.TargetApi;
+import android.os.Build;
+
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.chrome.browser.notifications.NotificationSettingsBridge;
+
+/**
+ * This class provides our native code to access NotificationSettingsBridge
+ * without patching notification_channels_provider_android.cc/h.
+ */
+public class BraveNotificationSettingsBridge {
+    @TargetApi(Build.VERSION_CODES.O)
+    @CalledByNative
+    static @NotificationChannelStatus int getChannelStatus(String channelId) {
+        return NotificationSettingsBridge.getChannelStatus(channelId);
+    }
+}

build/android/BUILD.gn

@@ -96,6 +96,7 @@ generate_jni("jni_headers") {
     "//brave/android/java/org/chromium/chrome/browser/BraveActivity.java",
     "//brave/android/java/org/chromium/chrome/browser/BraveRelaunchUtils.java",
     "//brave/android/java/org/chromium/chrome/browser/BraveRewardsNativeWorker.java",
+    "//brave/android/java/org/chromium/chrome/browser/notifications/BraveNotificationSettingsBridge.java",
     "//brave/android/java/org/chromium/chrome/browser/preferences/BravePrefServiceBridge.java",
     "//brave/android/java/org/chromium/chrome/browser/preferences/website/BraveShieldsContentSettings.java",
     "//brave/android/java/org/chromium/chrome/browser/signin/BraveSigninManager.java",

components/brave_ads/browser/notification_helper_android.cc

@@ -3,15 +3,18 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#include "brave/components/brave_ads/browser/notification_helper_android.h"
+
 #include <string>
 
 #include "base/android/jni_string.h"
 #include "base/system/sys_info.h"
-#include "brave/components/brave_ads/browser/notification_helper_android.h"
 #include "brave/build/android/jni_headers/BraveAds_jni.h"
 #include "brave/build/android/jni_headers/BraveAdsSignupDialog_jni.h"
+#include "brave/build/android/jni_headers/BraveNotificationSettingsBridge_jni.h"
 #include "brave/components/brave_ads/browser/background_helper.h"
 #include "chrome/android/chrome_jni_headers/NotificationSystemStatusUtil_jni.h"
+#include "chrome/browser/notifications/notification_channels_provider_android.h"
 
 namespace brave_ads {
 
@@ -77,13 +80,12 @@ bool NotificationHelperAndroid::IsBraveAdsNotificationChannelEnabled() const {
 
   JNIEnv* env = base::android::AttachCurrentThread();
   auto j_channel_id = Java_BraveAds_getBraveAdsChannelId(env);
-  std::string channel_id = ConvertJavaStringToUTF8(env, j_channel_id);
+  auto status = static_cast<NotificationChannelStatus>(
+      Java_BraveNotificationSettingsBridge_getChannelStatus(
+          env, j_channel_id));
 
-  return false;
-  // TODO(jocelyn): FIXME
-  // auto status = channels_provider_->GetChannelStatus(channel_id);
-  // return (status == NotificationChannelStatus::ENABLED ||
-  //    status == NotificationChannelStatus::UNAVAILABLE);
+  return (status == NotificationChannelStatus::ENABLED ||
+      status == NotificationChannelStatus::UNAVAILABLE);
 }
 
 int NotificationHelperAndroid::GetOperatingSystemVersion() const {

components/brave_ads/browser/notification_helper_android.h

@@ -11,7 +11,6 @@
 #include "base/memory/weak_ptr.h"
 
 #include "brave/components/brave_ads/browser/notification_helper.h"
-#include "chrome/browser/notifications/notification_channels_provider_android.h"
 
 namespace brave_ads {
 
@@ -27,9 +26,6 @@ class NotificationHelperAndroid
 
   bool IsBraveAdsNotificationChannelEnabled() const;
 
-  std::unique_ptr<NotificationChannelsProviderAndroid> channels_provider_ =
-      std::make_unique<NotificationChannelsProviderAndroid>();
-
   int GetOperatingSystemVersion() const;
 
   // NotificationHelper impl