Log some information about the state of the homepage on Android.

chrome/browser/prefs/pref_metrics_service.h

 // Copyright 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.
 
 #ifndef CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_
 #define CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/syncable_prefs/synced_pref_change_registrar.h"
 
 class PrefRegistrySimple;
 
 // PrefMetricsService is responsible for recording prefs-related UMA stats.
 class PrefMetricsService : public KeyedService {
  public:
   explicit PrefMetricsService(Profile* profile);
   ~PrefMetricsService() override;
 
+  // Records metrics about the state of the homepage on launch.  On all
+  // platforms except Android this will be triggered automatically as part of
+  // initializing the PrefMetricsService.  On Android, the state of the
+  // homepage is determined by external providers on the device, so this will

[Mark P, 2016/05/24 18:41:53]

"determined by external providers on the device"
is vague.
Perhaps, something like "set by third parties is stored in XYZ (outside of
Chrome)"

[Ted C, 2016/05/24 19:01:33]

Done.

+  // be triggered once all the information can be collected.
+  static void RecordHomePageLaunchMetrics(bool show_home_button,
+                                          bool homepage_is_ntp,
+                                          const GURL& homepage_url);
+
   class Factory : public BrowserContextKeyedServiceFactory {
    public:
     static Factory* GetInstance();
     static PrefMetricsService* GetForProfile(Profile* profile);
    private:
     friend struct base::DefaultSingletonTraits<Factory>;
 
     Factory();
     ~Factory() override;
 
@@ skipping 48 matching lines @@
 
   std::unique_ptr<syncable_prefs::SyncedPrefChangeRegistrar>
       synced_pref_change_registrar_;
 
   base::WeakPtrFactory<PrefMetricsService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefMetricsService);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_