Rename DesktopEngagement* to DesktopSessionDuration*.

chrome/browser/metrics/desktop_session/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_engagement/chrome_visibility_observer.h"
+#include "chrome/browser/metrics/desktop_session/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_engagement/desktop_engagement_service.h"
+#include "chrome/browser/metrics/desktop_session/desktop_session_service.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "components/variations/variations_associated_data.h"
 
 namespace metrics {
 
 ChromeVisibilityObserver::ChromeVisibilityObserver() : weak_factory_(this) {
   BrowserList::AddObserver(this);
   InitVisibilityGapTimeout();
 }
 
 ChromeVisibilityObserver::~ChromeVisibilityObserver() {
   BrowserList::RemoveObserver(this);
 }
 
 void ChromeVisibilityObserver::SendVisibilityChangeEvent(bool active) {
-  DesktopEngagementService::Get()->OnVisibilityChanged(active);
+  DesktopSessionService::Get()->OnVisibilityChanged(active);
 }
 
 void ChromeVisibilityObserver::CancelVisibilityChange() {
   weak_factory_.InvalidateWeakPtrs();
 }
 
 void ChromeVisibilityObserver::OnBrowserSetLastActive(Browser* browser) {
   if (weak_factory_.HasWeakPtrs())
     CancelVisibilityChange();
   else
@@ skipping 15 matching lines @@
     CancelVisibilityChange();
     SendVisibilityChangeEvent(false);
   }
 }
 
 void ChromeVisibilityObserver::InitVisibilityGapTimeout() {
   const int kDefaultVisibilityGapTimeout = 3;
 
   int timeout_seconds = kDefaultVisibilityGapTimeout;
   std::string param_value = variations::GetVariationParamValue(
-      "DesktopEngagement", "visibility_gap_timeout");
+      "DesktopSession", "visibility_gap_timeout");

[dominickn, 2016/09/13 01:29:53]

I grepped the finch studies directory and found no instances of this string, so
I assume it's safe to rename. Please let me know if this assumption is
incorrect.

[gayane -on leave until 09-2017, 2016/09/13 17:09:29]

Thats correct the study doesn't exist at the moment. This code was added for
future in case we will need to play around with the default timeout intervals.
So its safe to rename.

   if (!param_value.empty())
     base::StringToInt(param_value, &timeout_seconds);
 
   visibility_gap_timeout_ = base::TimeDelta::FromSeconds(timeout_seconds);
 }
 
 }  // namespace metrics