Add metrics to keep track of the tab activate/deactivate cycle

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc

 // Copyright (c) 2013 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/chrome_browser_main_extra_parts_metrics.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 14 matching lines @@
 #include "content/public/browser/browser_thread.h"
 #include "ui/base/touch/touch_device.h"
 #include "ui/base/ui_base_switches.h"
 #include "ui/display/screen.h"
 #include "ui/events/event_switches.h"
 
 #if defined(OS_ANDROID) && defined(__arm__)
 #include <cpu-features.h>
 #endif  // defined(OS_ANDROID) && defined(__arm__)
 
+#if !defined(OS_ANDROID)
+#include "chrome/browser/metrics/tab_usage_recorder.h"
+#endif  // !defined(OS_ANDROID)
+
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS)
 #include <gnu/libc-version.h>
 
 #include "base/version.h"
 #if defined(USE_X11)
 #include "ui/base/x/x11_util.h"
 #endif
 #endif  // defined(OS_LINUX) && !defined(OS_CHROMEOS)
 
 #if defined(USE_OZONE) || defined(USE_X11)
@@ skipping 310 matching lines @@
   content::BrowserThread::PostDelayedTask(
       content::BrowserThread::IO, FROM_HERE,
       base::Bind(&shell_integration::win::RecordIsPinnedToTaskbarHistogram),
       kStartupMetricsGatheringDelay);
 #endif  // defined(OS_WIN)
 
   display_count_ = display::Screen::GetScreen()->GetNumDisplays();
   UMA_HISTOGRAM_COUNTS_100("Hardware.Display.Count.OnStartup", display_count_);
   display::Screen::GetScreen()->AddObserver(this);
   is_screen_observer_ = true;
+
+#if !defined(OS_ANDROID)
+  metrics::TabUsageRecorder::Initialize();
+#endif  // !defined(OS_ANDROID)
 }
 
 void ChromeBrowserMainExtraPartsMetrics::OnDisplayAdded(
     const display::Display& new_display) {
   EmitDisplaysChangedMetric();
 }
 
 void ChromeBrowserMainExtraPartsMetrics::OnDisplayRemoved(
     const display::Display& old_display) {
   EmitDisplaysChangedMetric();
@@ skipping 11 matching lines @@
   }
 }
 
 namespace chrome {
 
 void AddMetricsExtraParts(ChromeBrowserMainParts* main_parts) {
   main_parts->AddParts(new ChromeBrowserMainExtraPartsMetrics());
 }
 
 }  // namespace chrome