Introduce a new API to handle native notification clicks

chrome/browser/notifications/notification_platform_bridge_mac_unittest.mm

Index: chrome/browser/notifications/notification_platform_bridge_mac_unittest.mm
diff --git a/chrome/browser/notifications/notification_platform_bridge_mac_unittest.mm b/chrome/browser/notifications/notification_platform_bridge_mac_unittest.mm
index 509729a5db138ef14d2fbe42e534c1cde44bfd7f..fc12821b03232131eafed56089f538755253e330 100644
--- a/chrome/browser/notifications/notification_platform_bridge_mac_unittest.mm
+++ b/chrome/browser/notifications/notification_platform_bridge_mac_unittest.mm
@@ -26,6 +26,7 @@ NSMutableDictionary* BuildDefaultNotificationResponse() {
   [builder setNotificationId:@"notificationId"];
   [builder setProfileId:@"profileId"];
   [builder setIncognito:false];
+  [builder setNotificationType:[NSNumber numberWithInt:0]];
 
   NSUserNotification* notification = [builder buildUserNotification];
   return [NSMutableDictionary
@@ -40,6 +41,13 @@ TEST(NotificationPlatformBridgeMacTest, TestNotificationValidResponse) {
   EXPECT_TRUE(NotificationPlatformBridgeMac::VerifyNotificationData(response));
 }
 
+TEST(NotificationPlatformBridgeMacTest, TestNotificationUnknownType) {
+  NSMutableDictionary* response = BuildDefaultNotificationResponse();
+  [response setValue:[NSNumber numberWithInt:210581]
+              forKey:notification_constants::kNotificationType];
+  EXPECT_FALSE(NotificationPlatformBridgeMac::VerifyNotificationData(response));
+}
+
 TEST(NotificationPlatformBridgeMacTest, TestNotificationUnknownOperation) {
   NSMutableDictionary* response = BuildDefaultNotificationResponse();
   [response setValue:[NSNumber numberWithInt:40782]