Change logging of about:flags from actions to a histogram.

chrome/browser/about_flags.cc

 // Copyright (c) 2012 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/about_flags.h"
 
 #include <iterator>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 627 matching lines @@
 };
 
 const FeatureEntry::Choice kSSLVersionMaxChoices[] = {
     {IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT, "", "" },
     {IDS_FLAGS_SSL_VERSION_MAX_TLS12, switches::kSSLVersionMax, "tls1.2"},
     {IDS_FLAGS_SSL_VERSION_MAX_TLS13, switches::kSSLVersionMax, "tls1.3"},
 };
 
 // RECORDING USER METRICS FOR FLAGS:
 // -----------------------------------------------------------------------------
-// The first line of the entry is the internal name. If you'd like to gather
-// statistics about the usage of your flag, you should append a marker comment
-// to the end of the feature name, like so:
-//   "my-special-feature",  // FLAGS:RECORD_UMA
+// The first line of the entry is the internal name.
 //
-// After doing that, run
-//   tools/metrics/actions/extract_actions.py
-// to add the metric to actions.xml (which will enable UMA to record your
-// feature flag), then update the <owner>s and <description> sections. Make sure
-// to include the actions.xml file when you upload your code for review!
-//
-// After your feature has shipped under a flag, you can locate the metrics under
-// the action name AboutFlags_internal-action-name. Actions are recorded once
-// per startup, so you should divide this number by AboutFlags_StartupTick to
-// get a sense of usage. Note that this will not be the same as number of users
-// with a given feature enabled because users can quit and relaunch the
-// application multiple times over a given time interval. The dashboard also
-// shows you how many (metrics reporting) users have enabled the flag over the
-// last seven days. However, note that this is not the same as the number of
-// users who have the flag enabled, since enabling the flag happens once,
-// whereas running with the flag enabled happens until the user flips the flag
-// again.
+// Usage of about:flags is logged on startup via the "AboutFlags.Seen" UMA
+// histogram. This histogram shows the number of startups with a given flag
+// enabled. If you'd like to see user counts instead, make sure to switch to
+// to "count users" view on the dashboard.

[Ilya Sherman, 2016/08/29 21:19:59]

nit: You repeat this below as well -- is that intended?

[Alexei Svitkine (slow), 2016/08/29 21:50:58]

Nope, removed!

 
 // To add a new entry, add to the end of kFeatureEntries. There are two
 // distinct types of entries:
 // . SINGLE_VALUE: entry is either on or off. Use the SINGLE_VALUE_TYPE
 //   macro for this type supplying the command line to the macro.
 // . MULTI_VALUE: a list of choices, the first of which should correspond to a
 //   deactivated state for this lab (i.e. no command line option).  To specify
 //   this type of entry use the macro MULTI_VALUE_TYPE supplying it the
 //   array of choices.
 // See the documentation of FeatureEntry for details on the fields.
 //
-// Command-line switches must have entries in enum "LoginCustomFlags" in
-// histograms.xml. See note in histograms.xml and don't forget to run
-// AboutFlagsHistogramTest unit test to calculate and verify checksum.
+// Usage of about:flags is logged on startup via the "AboutFlags.Seen" UMA
+// histogram. This histogram shows the number of startups with a given flag
+// enabled. If you'd like to see user counts instead, make sure to switch to
+// to "count users" view on the dashboard. When adding new entries, the enum
+// "LoginCustomFlags" must be updated in histograms.xml. See note in
+// histograms.xml and don't forget to run AboutFlagsHistogramTest unit test
+// to calculate and verify checksum.

[Ilya Sherman, 2016/08/29 21:19:58]

Hmm, the user actions measured how often users *switched* a given flag.  The
histogram is measuring the state at startup, which is a different thing.  Are
you sure that there aren't consumers of this data who are interested
specifically in how often flags are switched?

[Alexei Svitkine (slow), 2016/08/29 21:50:58]

I thought so too originally, but turns out they were logged at startup, in fact.

You can take a look at RecordUMAStatistics() which was logging them, whose
implementation I'm replacing in this CL.

 //
 // When adding a new choice, add it to the end of the list.
 const FeatureEntry kFeatureEntries[] = {
     {"ignore-gpu-blacklist", IDS_FLAGS_IGNORE_GPU_BLACKLIST_NAME,
      IDS_FLAGS_IGNORE_GPU_BLACKLIST_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kIgnoreGpuBlacklist)},
     {"enable-experimental-canvas-features",
      IDS_FLAGS_EXPERIMENTAL_CANVAS_FEATURES_NAME,
      IDS_FLAGS_EXPERIMENTAL_CANVAS_FEATURES_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableExperimentalCanvasFeatures)},
@@ skipping 27 matching lines @@
      IDS_FLAGS_WEBRTC_STUN_ORIGIN_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableWebRtcStunOrigin)},
 #endif
 #if defined(OS_ANDROID)
     {"enable-osk-overscroll", IDS_FLAGS_ENABLE_OSK_OVERSCROLL_NAME,
      IDS_FLAGS_ENABLE_OSK_OVERSCROLL_DESCRIPTION, kOsAndroid,
      SINGLE_VALUE_TYPE(switches::kEnableOSKOverscroll)},
 #endif
   // Native client is compiled out when DISABLE_NACL is defined.
 #if !defined(DISABLE_NACL)
-    {"enable-nacl",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_NACL_NAME, IDS_FLAGS_NACL_DESCRIPTION, kOsAll,
+    {"enable-nacl", IDS_FLAGS_NACL_NAME, IDS_FLAGS_NACL_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableNaCl)},
-    {"enable-nacl-debug",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_NACL_DEBUG_NAME, IDS_FLAGS_NACL_DEBUG_DESCRIPTION, kOsDesktop,
+    {"enable-nacl-debug", IDS_FLAGS_NACL_DEBUG_NAME,
+     IDS_FLAGS_NACL_DEBUG_DESCRIPTION, kOsDesktop,
      SINGLE_VALUE_TYPE(switches::kEnableNaClDebug)},
     {"force-pnacl-subzero", IDS_FLAGS_PNACL_SUBZERO_NAME,
      IDS_FLAGS_PNACL_SUBZERO_DESCRIPTION, kOsDesktop,
      SINGLE_VALUE_TYPE(switches::kForcePNaClSubzero)},
-    {"nacl-debug-mask",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_NACL_DEBUG_MASK_NAME, IDS_FLAGS_NACL_DEBUG_MASK_DESCRIPTION,
-     kOsDesktop, MULTI_VALUE_TYPE(kNaClDebugMaskChoices)},
+    {"nacl-debug-mask", IDS_FLAGS_NACL_DEBUG_MASK_NAME,
+     IDS_FLAGS_NACL_DEBUG_MASK_DESCRIPTION, kOsDesktop,
+     MULTI_VALUE_TYPE(kNaClDebugMaskChoices)},
 #endif
 #if defined(ENABLE_EXTENSIONS)
-    {"extension-apis",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_EXPERIMENTAL_EXTENSION_APIS_NAME,
+    {"extension-apis", IDS_FLAGS_EXPERIMENTAL_EXTENSION_APIS_NAME,
      IDS_FLAGS_EXPERIMENTAL_EXTENSION_APIS_DESCRIPTION, kOsDesktop,
      SINGLE_VALUE_TYPE(extensions::switches::kEnableExperimentalExtensionApis)},
     {"extensions-on-chrome-urls", IDS_FLAGS_EXTENSIONS_ON_CHROME_URLS_NAME,
      IDS_FLAGS_EXTENSIONS_ON_CHROME_URLS_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(extensions::switches::kExtensionsOnChromeURLs)},
 #endif
     {"enable-fast-unload", IDS_FLAGS_FAST_UNLOAD_NAME,
      IDS_FLAGS_FAST_UNLOAD_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableFastUnload)},
 #if defined(ENABLE_EXTENSIONS)
@@ skipping 11 matching lines @@
                                switches::kDisableContextualSearch)},
 #endif
     {"show-autofill-type-predictions",
      IDS_FLAGS_SHOW_AUTOFILL_TYPE_PREDICTIONS_NAME,
      IDS_FLAGS_SHOW_AUTOFILL_TYPE_PREDICTIONS_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(autofill::switches::kShowAutofillTypePredictions)},
     {"enable-credit-card-signin-promo",
      IDS_FLAGS_ENABLE_AUTOFILL_CREDIT_CARD_SIGNIN_PROMO_NAME,
      IDS_FLAGS_ENABLE_AUTOFILL_CREDIT_CARD_SIGNIN_PROMO_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(autofill::kAutofillCreditCardSigninPromo)},
-    {"smooth-scrolling",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_SMOOTH_SCROLLING_NAME, IDS_FLAGS_SMOOTH_SCROLLING_DESCRIPTION,
+    {"smooth-scrolling", IDS_FLAGS_SMOOTH_SCROLLING_NAME,
+     IDS_FLAGS_SMOOTH_SCROLLING_DESCRIPTION,
      // Mac has a separate implementation with its own setting to disable.
      kOsLinux | kOsCrOS | kOsWin | kOsAndroid,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableSmoothScrolling,
                                switches::kDisableSmoothScrolling)},
 #if defined(USE_AURA) || defined(OS_LINUX)
     {"overlay-scrollbars", IDS_FLAGS_OVERLAY_SCROLLBARS_NAME,
      IDS_FLAGS_OVERLAY_SCROLLBARS_DESCRIPTION,
      // Uses the system preference on Mac (a different implementation).
      // On Android, this is always enabled.
      kOsLinux | kOsCrOS | kOsWin,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableOverlayScrollbar,
                                switches::kDisableOverlayScrollbar)},
 #endif
     {// See http://crbug.com/120416 for how to remove this flag.
-     "save-page-as-mhtml",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_SAVE_PAGE_AS_MHTML_NAME,
+     "save-page-as-mhtml", IDS_FLAGS_SAVE_PAGE_AS_MHTML_NAME,
      IDS_FLAGS_SAVE_PAGE_AS_MHTML_DESCRIPTION, kOsMac | kOsWin | kOsLinux,
      SINGLE_VALUE_TYPE(switches::kSavePageAsMHTML)},
     {"mhtml-generator-option", IDS_FLAGS_MHTML_GENERATOR_OPTION_NAME,
      IDS_FLAGS_MHTML_GENERATOR_OPTION_DESCRIPTION, kOsMac | kOsWin | kOsLinux,
      MULTI_VALUE_TYPE(kMHTMLGeneratorOptionChoices)},
     {"enable-quic", IDS_FLAGS_QUIC_NAME, IDS_FLAGS_QUIC_DESCRIPTION, kOsAll,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableQuic, switches::kDisableQuic)},
     {"disable-javascript-harmony-shipping",
      IDS_FLAGS_JAVASCRIPT_HARMONY_SHIPPING_NAME,
      IDS_FLAGS_JAVASCRIPT_HARMONY_SHIPPING_DESCRIPTION, kOsAll,
@@ skipping 18 matching lines @@
      0,
 #endif
      SINGLE_DISABLE_VALUE_TYPE(switches::kDisableSoftwareRasterizer)},
     {"enable-gpu-rasterization", IDS_FLAGS_GPU_RASTERIZATION_NAME,
      IDS_FLAGS_GPU_RASTERIZATION_DESCRIPTION, kOsAll,
      MULTI_VALUE_TYPE(kEnableGpuRasterizationChoices)},
     {"gpu-rasterization-msaa-sample-count",
      IDS_FLAGS_GPU_RASTERIZATION_MSAA_SAMPLE_COUNT_NAME,
      IDS_FLAGS_GPU_RASTERIZATION_MSAA_SAMPLE_COUNT_DESCRIPTION, kOsAll,
      MULTI_VALUE_TYPE(kGpuRasterizationMSAASampleCountChoices)},
-    {"enable-experimental-web-platform-features",  // FLAGS:RECORD_UMA
+    {"enable-experimental-web-platform-features",
      IDS_FLAGS_EXPERIMENTAL_WEB_PLATFORM_FEATURES_NAME,
      IDS_FLAGS_EXPERIMENTAL_WEB_PLATFORM_FEATURES_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableExperimentalWebPlatformFeatures)},
-    {"enable-web-bluetooth",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_WEB_BLUETOOTH_NAME, IDS_FLAGS_WEB_BLUETOOTH_DESCRIPTION,
+    {"enable-web-bluetooth", IDS_FLAGS_WEB_BLUETOOTH_NAME,
+     IDS_FLAGS_WEB_BLUETOOTH_DESCRIPTION,
      kOsCrOS | kOsMac | kOsAndroid | kOsLinux,
      SINGLE_VALUE_TYPE(switches::kEnableWebBluetooth)},
 #if defined(ENABLE_EXTENSIONS)
     {"enable-ble-advertising-in-apps",
      IDS_FLAGS_BLE_ADVERTISING_IN_EXTENSIONS_NAME,
      IDS_FLAGS_BLE_ADVERTISING_IN_EXTENSIONS_DESCRIPTION, kOsCrOS,
      SINGLE_VALUE_TYPE(extensions::switches::kEnableBLEAdvertising)},
 #endif
     {"enable-devtools-experiments", IDS_FLAGS_DEVTOOLS_EXPERIMENTS_NAME,
      IDS_FLAGS_DEVTOOLS_EXPERIMENTS_DESCRIPTION, kOsDesktop,
@@ skipping 489 matching lines @@
 #endif
     {"translate-lang-by-ulp", IDS_FLAGS_TRANSLATE_LANGUAGE_BY_ULP_NAME,
      IDS_FLAGS_TRANSLATE_LANGUAGE_BY_ULP_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(translate::kTranslateLanguageByULP)},
 #if defined(OS_MACOSX)
     {"enable-native-notifications", IDS_NOTIFICATIONS_NATIVE_FLAG,
      IDS_NOTIFICATIONS_NATIVE_FLAG_DESCRIPTION, kOsMac,
      SINGLE_VALUE_TYPE(switches::kEnableNativeNotifications)},
 #endif
 #if defined(TOOLKIT_VIEWS)
-    {"disable-views-rect-based-targeting",  // FLAGS:RECORD_UMA
+    {"disable-views-rect-based-targeting",
      IDS_FLAGS_VIEWS_RECT_BASED_TARGETING_NAME,
      IDS_FLAGS_VIEWS_RECT_BASED_TARGETING_DESCRIPTION,
      kOsCrOS | kOsWin | kOsLinux,
      SINGLE_DISABLE_VALUE_TYPE(
          views::switches::kDisableViewsRectBasedTargeting)},
 #endif
 #if defined(ENABLE_EXTENSIONS)
     {"enable-apps-show-on-first-paint", IDS_FLAGS_APPS_SHOW_ON_FIRST_PAINT_NAME,
      IDS_FLAGS_APPS_SHOW_ON_FIRST_PAINT_DESCRIPTION, kOsDesktop,
      SINGLE_VALUE_TYPE(extensions::switches::kEnableAppsShowOnFirstPaint)},
@@ skipping 158 matching lines @@
 #if defined(OS_ANDROID)
     {"enable-seccomp-sandbox-android",
      IDS_FLAGS_SECCOMP_FILTER_SANDBOX_ANDROID_NAME,
      IDS_FLAGS_SECCOMP_FILTER_SANDBOX_ANDROID_DESCRIPTION, kOsAndroid,
      FEATURE_VALUE_TYPE(features::kSeccompSandboxAndroid)},
 #endif
     {"enable-touch-hover", IDS_FLAGS_TOUCH_HOVER_NAME,
      IDS_FLAGS_TOUCH_HOVER_DESCRIPTION, kOsAndroid,
      SINGLE_VALUE_TYPE("enable-touch-hover")},
 #if defined(OS_CHROMEOS)
-    {"enable-wifi-credential-sync",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_WIFI_CREDENTIAL_SYNC_NAME,
+    {"enable-wifi-credential-sync", IDS_FLAGS_WIFI_CREDENTIAL_SYNC_NAME,
      IDS_FLAGS_WIFI_CREDENTIAL_SYNC_DESCRIPTION, kOsCrOS,
      SINGLE_VALUE_TYPE(switches::kEnableWifiCredentialSync)},
     {"enable-potentially-annoying-security-features",
      IDS_FLAGS_EXPERIMENTAL_SECURITY_FEATURES_NAME,
      IDS_FLAGS_EXPERIMENTAL_SECURITY_FEATURES_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnablePotentiallyAnnoyingSecurityFeatures)},
 #endif
-    {"mark-non-secure-as",  // FLAGS:RECORD_UMA
-     IDS_MARK_NON_SECURE_AS_NAME, IDS_MARK_NON_SECURE_AS_DESCRIPTION, kOsAll,
+    {"mark-non-secure-as", IDS_MARK_NON_SECURE_AS_NAME,
+     IDS_MARK_NON_SECURE_AS_DESCRIPTION, kOsAll,
      MULTI_VALUE_TYPE(kMarkNonSecureAsChoices)},
     {"enable-site-per-process", IDS_FLAGS_SITE_PER_PROCESS_NAME,
      IDS_FLAGS_SITE_PER_PROCESS_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kSitePerProcess)},
     {"enable-top-document-isolation", IDS_FLAGS_TOP_DOCUMENT_ISOLATION_NAME,
      IDS_FLAGS_TOP_DOCUMENT_ISOLATION_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kTopDocumentIsolation)},
     {"enable-use-zoom-for-dsf", IDS_FLAGS_ENABLE_USE_ZOOM_FOR_DSF_NAME,
      IDS_FLAGS_ENABLE_USE_ZOOM_FOR_DSF_DESCRIPTION, kOsAll,
      MULTI_VALUE_TYPE(kEnableUseZoomForDSFChoices)},
@@ skipping 422 matching lines @@
      SINGLE_VALUE_TYPE(
          chromeos::switches::kEnableExperimentalAccessibilityFeatures)},
     {"opt-in-ime-menu", IDS_FLAGS_ENABLE_IME_MENU_NAME,
      IDS_FLAGS_ENABLE_IME_MENU_DESCRIPTION, kOsCrOS,
      FEATURE_VALUE_TYPE(features::kOptInImeMenu)},
     {"disable-system-timezone-automatic-detection",
      IDS_FLAGS_DISABLE_SYSTEM_TIMEZONE_AUTOMATIC_DETECTION_NAME,
      IDS_FLAGS_DISABLE_SYSTEM_TIMEZONE_AUTOMATIC_DETECTION_DESCRIPTION, kOsCrOS,
      SINGLE_VALUE_TYPE(
          chromeos::switches::kDisableSystemTimezoneAutomaticDetectionPolicy)},
-    {"enable-native-cups",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_ENABLE_NATIVE_CUPS_NAME,
+    {"enable-native-cups", IDS_FLAGS_ENABLE_NATIVE_CUPS_NAME,
      IDS_FLAGS_ENABLE_NATIVE_CUPS_DESCRIPTION, kOsCrOS,
      SINGLE_VALUE_TYPE(switches::kEnableNativeCups)},
     {"enable-files-details-panel", IDS_FLAGS_ENABLE_FILES_DETAILS_PANEL_NAME,
      IDS_FLAGS_ENABLE_FILES_DETAILS_PANEL_DESCRIPTION, kOsCrOS,
      SINGLE_VALUE_TYPE(chromeos::switches::kEnableFilesDetailsPanel)},
 #endif // defined(OS_CHROMEOS)
 #if !defined(OS_ANDROID) && !defined(OS_IOS) && defined(GOOGLE_CHROME_BUILD)
     {"enable-google-branded-context-menu",
      IDS_FLAGS_GOOGLE_BRANDED_CONTEXT_MENU_NAME,
      IDS_FLAGS_GOOGLE_BRANDED_CONTEXT_MENU_DESCRIPTION, kOsDesktop,
@@ skipping 11 matching lines @@
      SINGLE_VALUE_TYPE(switches::kEnableFullscreenToolbarReveal)},
 #endif
 #if defined(OS_ANDROID)
     {"important-sites-in-cbd", IDS_FLAGS_IMPORTANT_SITES_IN_CBD_NAME,
      IDS_FLAGS_IMPORTANT_SITES_IN_CBD_DESCRIPTION, kOsAndroid,
      FEATURE_VALUE_TYPE(chrome::android::kImportantSitesInCBD)},
     {"autoplay-muted-videos", IDS_FLAGS_ENABLE_AUTOPLAY_MUTED_VIDEOS_NAME,
      IDS_FLAGS_ENABLE_AUTOPLAY_MUTED_VIDEOS_DESCRIPTION, kOsAndroid,
      FEATURE_VALUE_TYPE(features::kAutoplayMutedVideos)},
 #endif
-    {"enable-pointer-events",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_EXPERIMENTAL_POINTER_EVENT_NAME,
+    {"enable-pointer-events", IDS_FLAGS_EXPERIMENTAL_POINTER_EVENT_NAME,
      IDS_FLAGS_EXPERIMENTAL_POINTER_EVENT_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kPointerEvents)},
-    {"passive-listener-default",  // FLAGS:RECORD_UMA
-     IDS_FLAGS_PASSIVE_EVENT_LISTENER_DEFAULT_NAME,
+    {"passive-listener-default", IDS_FLAGS_PASSIVE_EVENT_LISTENER_DEFAULT_NAME,
      IDS_FLAGS_PASSIVE_EVENT_LISTENER_DEFAULT_DESCRIPTION, kOsAll,
      MULTI_VALUE_TYPE(kPassiveListenersChoices)},
-    {"document-passive-event-listeners",  // FLAGS:RECORD_UMA
+    {"document-passive-event-listeners",
      IDS_FLAGS_PASSIVE_DOCUMENT_EVENT_LISTENERS_NAME,
      IDS_FLAGS_PASSIVE_DOCUMENT_EVENT_LISTENERS_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kPassiveDocumentEventListeners)},
-    {"passive-event-listeners-due-to-fling",  // FLAGS:RECORD_UMA
+    {"passive-event-listeners-due-to-fling",
      IDS_FLAGS_PASSIVE_EVENT_LISTENERS_DUE_TO_FLING_NAME,
      IDS_FLAGS_PASSIVE_EVENT_LISTENERS_DUE_TO_FLING_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kPassiveEventListenersDueToFling)},
     {"enable-loading-ipc-optimization-for-small-resources",
      IDS_FLAGS_OPTIMIZE_LOADING_IPC_FOR_SMALL_RESOURCES_NAME,
      IDS_FLAGS_OPTIMIZE_LOADING_IPC_FOR_SMALL_RESOURCES_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kOptimizeLoadingIPCForSmallResources)},
     {"enable-font-cache-scaling", IDS_FLAGS_FONT_CACHE_SCALING_NAME,
      IDS_FLAGS_FONT_CACHE_SCALING_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kFontCacheScaling)},
@@ skipping 11 matching lines @@
      IDS_FLAGS_ENABLE_WEAK_MEMORYCACHE_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kWeakMemoryCache)},
 #if defined(OS_CHROMEOS)
     {"disable-eol-notification", IDS_FLAGS_EOL_NOTIFICATION_NAME,
      IDS_FLAGS_EOL_NOTIFICATION_DESCRIPTION, kOsCrOS,
      SINGLE_DISABLE_VALUE_TYPE(chromeos::switches::kDisableEolNotification)},
 #endif  // defined(OS_CHROMEOS)
     {"fill-on-account-select", IDS_FILL_ON_ACCOUNT_SELECT_NAME,
      IDS_FILL_ON_ACCOUNT_SELECT_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(password_manager::features::kFillOnAccountSelect)},
-    {"new-audio-rendering-mixing-strategy",  // FLAGS:RECORD_UMA
+    {"new-audio-rendering-mixing-strategy",
      IDS_NEW_AUDIO_RENDERING_MIXING_STRATEGY_NAME,
      IDS_NEW_AUDIO_RENDERING_MIXING_STRATEGY_DESCRIPTION,
      kOsWin | kOsMac | kOsLinux | kOsAndroid,
      FEATURE_VALUE_TYPE(media::kNewAudioRenderingMixingStrategy)},
 #if defined(OS_CHROMEOS)
     {"files-quick-view", IDS_FLAGS_FILES_QUICK_VIEW_NAME,
      IDS_FLAGS_FILES_QUICK_VIEW_DESCRIPTION, kOsCrOS,
      ENABLE_DISABLE_VALUE_TYPE(chromeos::switches::kEnableFilesQuickView,
                                chromeos::switches::kDisableFilesQuickView)},
     {"quick-unlock-pin", IDS_FLAGS_QUICK_UNLOCK_PIN,
@@ skipping 70 matching lines @@
       channel != version_info::Channel::BETA &&
       channel != version_info::Channel::DEV &&
       channel != version_info::Channel::CANARY &&
       channel != version_info::Channel::UNKNOWN) {
     return true;
   }
 
   return false;
 }
 
+void ReportSingleFlagToHistogram(const std::string& uma_histogram_hame,
+                                 const std::string& flag) {
+  int uma_id = about_flags::testing::kBadSwitchFormatHistogramId;
+  if (base::StartsWith(flag, "--", base::CompareCase::SENSITIVE)) {
+    // Skip '--' before switch name.
+    std::string switch_name(flag.substr(2));
+
+    // Kill value, if any.
+    const size_t value_pos = switch_name.find('=');
+    if (value_pos != std::string::npos)
+      switch_name.resize(value_pos);
+
+    uma_id = GetSwitchUMAId(switch_name);
+  } else {
+    NOTREACHED() << "ReportSingleFlagToHistogram(): flag '" << flag
+                 << "' has incorrect format.";
+  }
+  DVLOG(1) << "ReportSingleFlagToHistogram(): histogram='" << uma_histogram_hame
+           << "' '" << flag << "', uma_id=" << uma_id;
+
+  // Sparse histogram macro does not cache the histogram, so it's safe
+  // to use macro with non-static histogram name here.
+  UMA_HISTOGRAM_SPARSE_SLOWLY(uma_histogram_hame, uma_id);
+}
+
 }  // namespace
 
 void ConvertFlagsToSwitches(flags_ui::FlagsStorage* flags_storage,
                             base::CommandLine* command_line,
                             flags_ui::SentinelsMode sentinels) {
   if (command_line->HasSwitch(switches::kNoExperiments))
     return;
 
   FlagsStateSingleton::GetFlagsState()->ConvertFlagsToSwitches(
       flags_storage, command_line, sentinels, switches::kEnableFeatures,
@@ skipping 50 matching lines @@
   FlagsStateSingleton::GetFlagsState()->RemoveFlagsSwitches(switch_list);
 }
 
 void ResetAllFlags(flags_ui::FlagsStorage* flags_storage) {
   FlagsStateSingleton::GetFlagsState()->ResetAllFlags(flags_storage);
 }
 
 void RecordUMAStatistics(flags_ui::FlagsStorage* flags_storage) {
   std::set<std::string> flags = flags_storage->GetFlags();
   for (const std::string& flag : flags) {
-    std::string action("AboutFlags_");
-    action += flag;
-    content::RecordComputedAction(action);
+    ReportSingleFlagToHistogram("AboutFlags.Seen", flag);
   }

[Ilya Sherman, 2016/08/29 21:19:59]

nit: Why not call ReportCustomFlags("AboutFlags.Seen", flags)?  (And maybe
rename that function?)

[Alexei Svitkine (slow), 2016/08/29 21:50:58]

Done.

-  // Since flag metrics are recorded every startup, add a tick so that the
-  // stats can be made meaningful.
-  if (flags.size())
-    content::RecordAction(base::UserMetricsAction("AboutFlags_StartupTick"));
-  content::RecordAction(base::UserMetricsAction("StartupTick"));
 }
 
 base::HistogramBase::Sample GetSwitchUMAId(const std::string& switch_name) {
   return static_cast<base::HistogramBase::Sample>(
       base::HashMetricName(switch_name));
 }
 
-void ReportCustomFlags(const std::string& uma_histogram_hame,
+void ReportCustomFlags(const std::string& uma_histogram_name,
                        const std::set<std::string>& command_line_difference) {
   for (const std::string& flag : command_line_difference) {
-    int uma_id = about_flags::testing::kBadSwitchFormatHistogramId;
-    if (base::StartsWith(flag, "--", base::CompareCase::SENSITIVE)) {
-      // Skip '--' before switch name.
-      std::string switch_name(flag.substr(2));
-
-      // Kill value, if any.
-      const size_t value_pos = switch_name.find('=');
-      if (value_pos != std::string::npos)
-        switch_name.resize(value_pos);
-
-      uma_id = GetSwitchUMAId(switch_name);
-    } else {
-      NOTREACHED() << "ReportCustomFlags(): flag '" << flag
-                   << "' has incorrect format.";
-    }
-    DVLOG(1) << "ReportCustomFlags(): histogram='" << uma_histogram_hame
-             << "' '" << flag << "', uma_id=" << uma_id;
-
-    // Sparse histogram macro does not cache the histogram, so it's safe
-    // to use macro with non-static histogram name here.
-    UMA_HISTOGRAM_SPARSE_SLOWLY(uma_histogram_hame, uma_id);
+    ReportSingleFlagToHistogram(uma_histogram_name, flag);
   }
 }
 
 namespace testing {
 
 const base::HistogramBase::Sample kBadSwitchFormatHistogramId = 0;
 
 const FeatureEntry* GetFeatureEntries(size_t* count) {
   *count = arraysize(kFeatureEntries);
   return kFeatureEntries;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags