[DesktopSessionDurationTracker] Remove visibility-switch timeout from session length.

chrome/browser/metrics/desktop_session_duration/chrome_visibility_observer.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/metrics/desktop_session_duration/chrome_visibility_observer.h"
 
 #include "base/memory/singleton.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "chrome/browser/metrics/desktop_session_duration/desktop_session_duration_tracker.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "components/variations/variations_associated_data.h"
 
 namespace metrics {
 
+namespace {
+
+const base::TimeDelta kZeroTime = base::TimeDelta::FromSeconds(0);
+
+}  // namespace
+
 ChromeVisibilityObserver::ChromeVisibilityObserver() : weak_factory_(this) {
   BrowserList::AddObserver(this);
   InitVisibilityGapTimeout();
 }
 
 ChromeVisibilityObserver::~ChromeVisibilityObserver() {
   BrowserList::RemoveObserver(this);
 }
 
-void ChromeVisibilityObserver::SendVisibilityChangeEvent(bool active) {
-  DesktopSessionDurationTracker::Get()->OnVisibilityChanged(active);
+void ChromeVisibilityObserver::SendVisibilityChangeEvent(
+    bool active,
+    base::TimeDelta time_ago) {
+  DesktopSessionDurationTracker::Get()->OnVisibilityChanged(active, time_ago);
 }
 
 void ChromeVisibilityObserver::CancelVisibilityChange() {
   weak_factory_.InvalidateWeakPtrs();
 }
 
 void ChromeVisibilityObserver::OnBrowserSetLastActive(Browser* browser) {
   if (weak_factory_.HasWeakPtrs())
     CancelVisibilityChange();
   else
-    SendVisibilityChangeEvent(true);
+    SendVisibilityChangeEvent(true, kZeroTime);
 }
 
 void ChromeVisibilityObserver::OnBrowserNoLongerActive(Browser* browser) {
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&ChromeVisibilityObserver::SendVisibilityChangeEvent,
-                 weak_factory_.GetWeakPtr(), false),
+                 weak_factory_.GetWeakPtr(), false, visibility_gap_timeout_),
       visibility_gap_timeout_);
 }
 
 void ChromeVisibilityObserver::OnBrowserRemoved(Browser* browser) {
   // If there are no browser instances left then we should notify that browser
   // is not visible anymore immediately without waiting.
   if (BrowserList::GetInstance()->empty()) {
     CancelVisibilityChange();
-    SendVisibilityChangeEvent(false);
+    SendVisibilityChangeEvent(false, kZeroTime);
   }
 }
 
 void ChromeVisibilityObserver::InitVisibilityGapTimeout() {
   const int kDefaultVisibilityGapTimeout = 3;
 
   int timeout_seconds = kDefaultVisibilityGapTimeout;
   std::string param_value = variations::GetVariationParamValue(
       "DesktopSessionDuration", "visibility_gap_timeout");
   if (!param_value.empty())
     base::StringToInt(param_value, &timeout_seconds);
 
   visibility_gap_timeout_ = base::TimeDelta::FromSeconds(timeout_seconds);
 }
 
 }  // namespace metrics