Record stats about kExtensionKnownDisabled with the PrefMetricsService.

chrome/browser/prefs/pref_metrics_service.cc

 // 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.
 
 #include "chrome/browser/prefs/pref_metrics_service.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_number_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browser_shutdown.h"
 // Accessing the Device ID API here is a layering violation.
 // TODO(bbudge) Move the API so it's usable here.
 // http://crbug.com/276485
 #include "chrome/browser/extensions/api/music_manager_private/device_id.h"
-#include "chrome/browser/extensions/extension_prefs.h"
 #include "chrome/browser/prefs/pref_service_syncable.h"
 #include "chrome/browser/prefs/scoped_user_pref_update.h"
 #include "chrome/browser/prefs/session_startup_pref.h"
 #include "chrome/browser/prefs/synced_pref_change_registrar.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search_engines/template_url_prepopulate_data.h"
 #include "chrome/browser/ui/tabs/pinned_tab_codec.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "components/browser_context_keyed_service/browser_context_dependency_manager.h"
 #include "crypto/hmac.h"
 #include "grit/browser_resources.h"
 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
 #include "ui/base/resource/resource_bundle.h"
 
 namespace {
 
 const int kSessionStartupPrefValueMax = SessionStartupPref::kPrefValueMax;
 
+// An unregistered preference to fill in indices in kTrackedPrefs below for
+// preferences that aren't defined on every platform. This is fine as the code
+// below (e.g. CheckTrackedPreferences()) skips unregistered preferences and
+// should thus never report any data about that index on the platforms where
+// that preference is unimplemented.
+const char kUnregisteredPreference[] = "_";
+
 // These preferences must be kept in sync with the TrackedPreference enum in
 // tools/metrics/histograms/histograms.xml. To add a new preference, append it
 // to the array and add a corresponding value to the histogram enum.
 const char* kTrackedPrefs[] = {
   prefs::kShowHomeButton,
   prefs::kHomePageIsNewTabPage,
   prefs::kHomePage,
   prefs::kRestoreOnStartup,
   prefs::kURLsToRestoreOnStartup,
   prefs::kExtensionsPref,
   prefs::kGoogleServicesLastUsername,
   prefs::kSearchProviderOverrides,
   prefs::kDefaultSearchProviderSearchURL,
   prefs::kDefaultSearchProviderKeyword,
   prefs::kDefaultSearchProviderName,
 #if !defined(OS_ANDROID)
   prefs::kPinnedTabs,
+#else
+  kUnregisteredPreference,
 #endif
+  prefs::kExtensionKnownDisabled,
 };
 
 static const size_t kSHA256DigestSize = 32;
 
 }  // namespace

[Bernhard Bauer, 2013/10/16 12:45:38]

Nit: Everything in here is const, which automatically gets internal linkage, so
the anonymous namespace isn't really necessary (and neither is the `static` two
lines above).

[gab, 2013/10/16 13:22:17]

I'm happy to clean this up in a follow-up CL, I agree that we should remove the
static two lines above as its redundant with the unnamed namespace, but I like
keeping the unnamed namespace itself to be explicit about the internal scope of
those variables (such is the style in most files in Chromium AFAIK).

WDYT?

 
 PrefMetricsService::PrefMetricsService(Profile* profile)
     : profile_(profile),
       prefs_(profile_->GetPrefs()),
       local_state_(g_browser_process->local_state()),
       profile_name_(profile_->GetPath().AsUTF8Unsafe()),
       tracked_pref_paths_(kTrackedPrefs),
       tracked_pref_path_count_(arraysize(kTrackedPrefs)),
       checked_tracked_prefs_(false),
       weak_factory_(this) {
@@ skipping 378 matching lines @@
 }
 
 bool PrefMetricsService::Factory::ServiceIsNULLWhileTesting() const {
   return false;
 }
 
 content::BrowserContext* PrefMetricsService::Factory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }