Add vlog for debugging

Added two very infreqent vlog for debug auth issues.

Bug: b:111370621
Test: locally build
Change-Id: I77d3f6cc23a8c0cd9d5ab30c59989d1f2d80b464
Reviewed-on: https://chromium-review.googlesource.com/1162879Reviewed-by: Tao Wu <wutao@chromium.org>
Commit-Queue: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580930}

chromeos/services/assistant/assistant_manager_service_impl.cc

@@ -99,6 +99,7 @@ AssistantManagerService::State AssistantManagerServiceImpl::GetState() const {
 
 void AssistantManagerServiceImpl::SetAccessToken(
     const std::string& access_token) {
+  VLOG(1) << "Set access token.";
   // Push the |access_token| we got as an argument into AssistantManager before
   // starting to ensure that all server requests will be authenticated once
   // it is started. |user_id| is used to pair a user to their |access_token|,

chromeos/services/assistant/service.cc

@@ -179,6 +179,7 @@ void Service::BindAssistantSettingsManager(
 }
 
 void Service::RequestAccessToken() {
+  VLOG(1) << "Start requesting access token.";
   GetIdentityManager()->GetPrimaryAccountInfo(base::BindOnce(
       &Service::GetPrimaryAccountInfoCallback, base::Unretained(this)));
 }