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

chrome/browser/prefs/pref_metrics_service.cc

Index: chrome/browser/prefs/pref_metrics_service.cc
diff --git a/chrome/browser/prefs/pref_metrics_service.cc b/chrome/browser/prefs/pref_metrics_service.cc
index 54ee8505c59947eac378c7a6405f4ee6d2532bc2..49c0fb0681f5ab69c88e0388c31d5ebbf9b2b511 100644
--- a/chrome/browser/prefs/pref_metrics_service.cc
+++ b/chrome/browser/prefs/pref_metrics_service.cc
@@ -78,13 +78,14 @@ PrefMetricsService::PrefMetricsService(Profile* profile,
 PrefMetricsService::~PrefMetricsService() {
 }
 
-void PrefMetricsService::RecordLaunchPrefs() {
-  bool show_home_button = prefs_->GetBoolean(prefs::kShowHomeButton);
-  bool home_page_is_ntp = prefs_->GetBoolean(prefs::kHomePageIsNewTabPage);
+// static
+void PrefMetricsService::RecordHomePageLaunchMetrics(bool show_home_button,
+                                                     bool homepage_is_ntp,
+                                                     const GURL& homepage_url) {
   UMA_HISTOGRAM_BOOLEAN("Settings.ShowHomeButton", show_home_button);
   if (show_home_button) {
     UMA_HISTOGRAM_BOOLEAN("Settings.GivenShowHomeButton_HomePageIsNewTabPage",
-                          home_page_is_ntp);
+                          homepage_is_ntp);
   }
 
   // For non-NTP homepages, see if the URL comes from the same TLD+1 as a known
@@ -94,8 +95,7 @@ void PrefMetricsService::RecordLaunchPrefs() {
   // (pages that share a TLD+1 with a known engine but aren't actually search
   // pages, e.g. plus.google.com).  Additionally, record the TLD+1 of non-NTP
   // homepages through the privacy-preserving Rappor service.
-  if (!home_page_is_ntp) {
-    GURL homepage_url(prefs_->GetString(prefs::kHomePage));
+  if (!homepage_is_ntp) {
     if (homepage_url.is_valid()) {
       UMA_HISTOGRAM_ENUMERATION(
           "Settings.HomePageEngineType",
@@ -106,9 +106,28 @@ void PrefMetricsService::RecordLaunchPrefs() {
           homepage_url);
     }
   }
+}
 
+void PrefMetricsService::RecordLaunchPrefs() {

[gab, 2016/05/25 14:03:24]

How about #if !defined(OS_ANDROID) on this entire method (with a meta-comment
explaining why each subsection either doesn't apply to Android or is done later
on Android)? Seems weird to have many ifdef blocks that amount to an empty body
on Android.

[Mark P, 2016/05/25 17:01:53]

I know it looks weird, but (i) these are independent decisions so I think they
should look like independent decisions to people reading the code and (ii) when
someone comes to the code to glance at metrics recording, they usually only look
in the near vicinity, not, say, 50 lines up to see if there's an ifdef covering
something larger than what should be the single conceptual unit they're looking
at.  I like this current structure.

[gab, 2016/05/25 17:13:11]

Ok, works for me then.

+  // On Android, determining whether the homepage is enabled requires waiting
+  // for a response from a third party provider installed on the device.  So,
+  // it will be logged later once all the dependent information is available.
+  // See DeferredStartupHandler.java.
+#if !defined(OS_ANDROID)
+  GURL homepage_url(prefs_->GetString(prefs::kHomePage));
+  RecordHomePageLaunchMetrics(prefs_->GetBoolean(prefs::kShowHomeButton),
+                              prefs_->GetBoolean(prefs::kHomePageIsNewTabPage),
+                              homepage_url);
+#endif
+
+  // Android does not support overriding the NTP URL.
+#if !defined(OS_ANDROID)
   SampleNewTabPageURL(profile_);
+#endif
 
+  // Tab restoring is always done on Android, so these metrics are not
+  // applicable.  Also, startup pages are not supported on Android
+#if !defined(OS_ANDROID)
   int restore_on_startup = prefs_->GetInteger(prefs::kRestoreOnStartup);
   UMA_HISTOGRAM_ENUMERATION("Settings.StartupPageLoadSettings",
                             restore_on_startup, kSessionStartupPrefValueMax);
@@ -136,7 +155,9 @@ void PrefMetricsService::RecordLaunchPrefs() {
       }
     }
   }
+#endif
 
+  // Android does not support pinned tabs.
 #if !defined(OS_ANDROID)
   StartupTabs startup_tabs = PinnedTabCodec::ReadPinnedTabs(profile_);
   UMA_HISTOGRAM_CUSTOM_COUNTS("Settings.PinnedTabs",