| Index: chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc | 
| diff --git a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc | 
| index 9be497ed78fe9e1b116e1177a63150ac28562ccf..151cae2b09a7ada3908e12ae6c76eaae304a8a6e 100644 | 
| --- a/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc | 
| +++ b/chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc | 
| @@ -21,6 +21,9 @@ | 
| #include "chrome/browser/chrome_browser_main.h" | 
| #include "chrome/browser/mac/bluetooth_utility.h" | 
| #include "chrome/browser/shell_integration.h" | 
| +#include "chrome/browser/ui/browser.h" | 
| +#include "chrome/browser/ui/browser_list.h" | 
| +#include "chrome/browser/ui/tabs/tab_strip_model.h" | 
| #include "components/flags_ui/pref_service_flags_storage.h" | 
| #include "content/public/browser/browser_thread.h" | 
| #include "content/public/common/content_switches.h" | 
| @@ -354,6 +357,8 @@ ChromeBrowserMainExtraPartsMetrics::ChromeBrowserMainExtraPartsMetrics() | 
| ChromeBrowserMainExtraPartsMetrics::~ChromeBrowserMainExtraPartsMetrics() { | 
| if (is_screen_observer_) | 
| display::Screen::GetScreen()->RemoveObserver(this); | 
| +  for (auto* browser : *BrowserList::GetInstance()) | 
| +    browser->tab_strip_model()->RemoveObserver(this); | 
| } | 
|  | 
| void ChromeBrowserMainExtraPartsMetrics::PreProfileInit() { | 
| @@ -420,11 +425,32 @@ void ChromeBrowserMainExtraPartsMetrics::PostBrowserStart() { | 
| is_screen_observer_ = true; | 
|  | 
| #if !defined(OS_ANDROID) | 
| -  metrics::BeginFirstWebContentsProfiling(); | 
| +  const BrowserList* browser_list = BrowserList::GetInstance(); | 
| + | 
| +  auto first_browser = browser_list->begin(); | 
| +  if (first_browser != browser_list->end()) { | 
| +    TabStripModel* tab_strip = (*first_browser)->tab_strip_model(); | 
| +    DCHECK(tab_strip); | 
| +    if (tab_strip->empty()) { | 
| +      // Start web contents profiling later, when there will be a tab to profile | 
| +      tab_strip->AddObserver(this); | 
| +    } else { | 
| +      metrics::BeginFirstWebContentsProfiling(); | 
| +    } | 
| +  } | 
| metrics::TabUsageRecorder::InitializeIfNeeded(); | 
| #endif  // !defined(OS_ANDROID) | 
| } | 
|  | 
| +void ChromeBrowserMainExtraPartsMetrics::TabInsertedAt( | 
| +    TabStripModel* tab_strip_model, | 
| +    content::WebContents* contents, | 
| +    int index, | 
| +    bool foreground) { | 
| +  metrics::BeginFirstWebContentsProfiling(); | 
| +  tab_strip_model->RemoveObserver(this); | 
| +} | 
| + | 
| void ChromeBrowserMainExtraPartsMetrics::OnDisplayAdded( | 
| const display::Display& new_display) { | 
| EmitDisplaysChangedMetric(); | 
|  |