Make shutdown support for keepalive requests more debuggable

The shutdown support for keepalive requests (issue 1147162) is not
working correctly on some environments. In order to make investigation
easier, this CL

 - adds some VLOGs, and
 - make the timeout value adjustable.

Bug: 1161996
Change-Id: Iccfd491e7fb244c32614221dbf0b96e9bd08d1b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2596591
Auto-Submit: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840501}

chrome/browser/chrome_content_browser_client.cc

@@ -704,10 +704,6 @@ using plugins::ChromeContentBrowserClientPluginsPart;
 
 namespace {
 
-#if !defined(OS_ANDROID)
-constexpr base::TimeDelta kKeepaliveDuration = base::TimeDelta::FromSeconds(1);
-#endif
-
 #if defined(OS_WIN) && !defined(COMPONENT_BUILD) && !defined(ADDRESS_SANITIZER)
 // Enables pre-launch Code Integrity Guard (CIG) for Chrome renderers, when
 // running on Windows 10 1511 and above. See
@@ -1305,6 +1301,19 @@ blink::UserAgentMetadata GetUserAgentMetadata() {
   return metadata;
 }
 
+#if !defined(OS_ANDROID)
+base::TimeDelta GetKeepaliveTimerTimeout() {
+  constexpr base::TimeDelta kDefaultValue = base::TimeDelta::FromSeconds(1);
+
+  const int seconds = base::GetFieldTrialParamByFeatureAsInt(
+      features::kShutdownSupportForKeepalive, "timeout", -1);
+  if (seconds < 0 || seconds > 60) {
+    return kDefaultValue;
+  }
+  return base::TimeDelta::FromSeconds(seconds);
+}
+#endif
+
 ChromeContentBrowserClient::ChromeContentBrowserClient() {
 #if BUILDFLAG(ENABLE_PLUGINS)
   extra_parts_.push_back(new ChromeContentBrowserClientPluginsPart);
@@ -5931,13 +5940,22 @@ ukm::UkmService* ChromeContentBrowserClient::GetUkmService() {
 void ChromeContentBrowserClient::OnKeepaliveRequestStarted() {
 #if !defined(OS_ANDROID)
   if (base::FeatureList::IsEnabled(features::kShutdownSupportForKeepalive)) {
+    // TODO(crbug.com/1161996): Remove this entry once the investigation is
+    // done.
+    VLOG(1) << "OnKeepaliveRequestStarted: " << num_keepalive_requests_
+            << " ==> " << num_keepalive_requests_ + 1;
     ++num_keepalive_requests_;
 
     DCHECK_GT(num_keepalive_requests_, 0u);
     last_keepalive_request_time_ = base::TimeTicks::Now();
     if (!keepalive_timer_.IsRunning()) {
+      const auto timeout = GetKeepaliveTimerTimeout();
+      // TODO(crbug.com/1161996): Remove this entry once the investigation is
+      // done.
+      VLOG(1) << "Starting a keepalive timer(" << timeout.InSecondsF()
+              << " seconds)";
       keepalive_timer_.Start(
-          FROM_HERE, kKeepaliveDuration,
+          FROM_HERE, timeout,
           base::BindOnce(
               &ChromeContentBrowserClient::OnKeepaliveTimerFired,
               weak_factory_.GetWeakPtr(),
@@ -5952,8 +5970,15 @@ void ChromeContentBrowserClient::OnKeepaliveRequestFinished() {
 #if !defined(OS_ANDROID)
   if (base::FeatureList::IsEnabled(features::kShutdownSupportForKeepalive)) {
     DCHECK_GT(num_keepalive_requests_, 0u);
+    // TODO(crbug.com/1161996): Remove this entry once the investigation is
+    // done.
+    VLOG(1) << "OnKeepaliveRequestFinished: " << num_keepalive_requests_
+            << " ==> " << num_keepalive_requests_ - 1;
     --num_keepalive_requests_;
     if (num_keepalive_requests_ == 0) {
+      // TODO(crbug.com/1161996): Remove this entry once the investigation is
+      // done.
+      VLOG(1) << "Stopping the keepalive timer";
       keepalive_timer_.Stop();
       // This deletes the keep alive handle attached to the timer function and
       // unblock the shutdown sequence.
@@ -6009,10 +6034,15 @@ ChromeContentBrowserClient::CreateIdentityRequestDialogController() {
 void ChromeContentBrowserClient::OnKeepaliveTimerFired(
     std::unique_ptr<ScopedKeepAlive> keep_alive_handle) {
 #if !defined(OS_ANDROID)
+  // TODO(crbug.com/1161996): Remove this entry once the investigation is done.
+  VLOG(1) << "OnKeepaliveTimerFired";
   DCHECK(base::FeatureList::IsEnabled(features::kShutdownSupportForKeepalive));
   const auto now = base::TimeTicks::Now();
-  const auto then = last_keepalive_request_time_ + kKeepaliveDuration;
+  const auto then = last_keepalive_request_time_ + GetKeepaliveTimerTimeout();
   if (now < then) {
+    // TODO(crbug.com/1161996): Remove this entry once the investigation is
+    // done.
+    VLOG(1) << "Extending keepalive timer";
     keepalive_timer_.Start(
         FROM_HERE, then - now,
         base::BindOnce(&ChromeContentBrowserClient::OnKeepaliveTimerFired,