Preset variation parameters for NTPSnippets feature.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index e966ebd31b89309f6f7edf76e277b35c0944688b..5d27c2e34fa361a928fd3524dd8ea8bdba6a43ed 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -44,6 +44,7 @@
 #include "components/flags_ui/flags_ui_switches.h"
 #include "components/nacl/common/nacl_switches.h"
 #include "components/network_session_configurator/switches.h"
+#include "components/ntp_snippets/ntp_snippets_constants.h"
 #include "components/ntp_tiles/switches.h"
 #include "components/offline_pages/offline_page_feature.h"
 #include "components/omnibox/browser/omnibox_switches.h"
@@ -512,6 +513,36 @@ const FeatureEntry::Choice kNtpSwitchToExistingTabChoices[] = {
 #endif  // defined(OS_ANDROID)
 
 #if defined(OS_ANDROID)
+const FeatureEntry::FeatureParam kNTPSnippetsFeatureVariationDefault[] = {
+    {"fetching_personalization", "both"},
+    {"fetching_host_restrict", "off"},

[Marc Treib, 2016/06/17 13:43:54]

Hm, the "Default" variant should probably not list any parameters? We already
have default values in the code for when the params are unset. Let's try to keep
the number of (potentially) different "defaults" to a minimum :)

[jkrcal, 2016/06/17 14:13:43]

Good point, done.
(I had actually to change the defaults in the code to match what was here.)

+};
+const FeatureEntry::FeatureParam kNTPSnippetsFeatureVariationOnlyPersonal[] = {
+    {"fetching_personalization", "personal"},
+    {"fetching_host_restrict", "off"},
+};
+const FeatureEntry::FeatureParam
+    kNTPSnippetsFeatureVariationOnlyNonPersonalHostRestricted[] = {
+        {"fetching_personalization", "non_personal"},
+        {"fetching_host_restrict", "on"},
+};
+const FeatureEntry::FeatureParam
+    kNTPSnippetsFeatureVariationOnlyPersonalHostRestricted[] = {
+        {"fetching_personalization", "personal"},
+        {"fetching_host_restrict", "on"},
+};
+
+const FeatureEntry::FeatureVariation kNTPSnippetsFeatureVariations[] = {
+    {"", kNTPSnippetsFeatureVariationDefault, 2},

[Marc Treib, 2016/06/17 13:43:54]

The "2"s here are for the number of parameters? Setting that explicitly seems
error-prone... but I don't see a good way of avoiding it.

[jkrcal, 2016/06/17 14:13:43]

I do not see it either as it is all statically defined.
(On the other hand, I am far from being a c++ guru, so feel free to prove me
wrong! :)

[Marc Treib, 2016/06/17 15:14:50]

Well, there's an arraysize() macro (in base/macros.h) which might be a bit nicer
than explicitly stating the number. It's not perfect because then you have to
spell the name twice.
Alternatively, it might be possible to do something with std::array, but a) I'm
not familiar enough with that to say for sure, and b) I'm not even sure it'd be
worth the effort.
So I'd probably just go with arraysize. Ultimately your call though; anyway it
should be pretty easy to diagnose if you specify a wrong number.

+    {"only personalized", kNTPSnippetsFeatureVariationOnlyPersonal, 2},
+    {"only from most visited sites",
+     kNTPSnippetsFeatureVariationOnlyNonPersonalHostRestricted, 2},
+    {"only personalized from most visited sites",
+     kNTPSnippetsFeatureVariationOnlyPersonalHostRestricted, 2},
+};
+#endif  // defined(OS_ANDROID)
+
+#if defined(OS_ANDROID)
 const FeatureEntry::Choice kUpdateMenuItemSummaryChoices[] = {
     {IDS_FLAGS_UPDATE_MENU_ITEM_NO_SUMMARY, "", ""},
     {IDS_FLAGS_UPDATE_MENU_ITEM_DEFAULT_SUMMARY,
@@ -1807,7 +1838,9 @@ const FeatureEntry kFeatureEntries[] = {
 #if defined(OS_ANDROID)
     {"enable-ntp-snippets", IDS_FLAGS_ENABLE_NTP_SNIPPETS_NAME,
      IDS_FLAGS_ENABLE_NTP_SNIPPETS_DESCRIPTION, kOsAndroid,
-     FEATURE_VALUE_TYPE(chrome::android::kNTPSnippetsFeature)},
+     FEATURE_WITH_VARIATIONS_VALUE_TYPE(chrome::android::kNTPSnippetsFeature,
+                                        kNTPSnippetsFeatureVariations,
+                                        ntp_snippets::kStudyName)},
 #endif  // defined(OS_ANDROID)
 #if defined(ENABLE_WEBRTC) && BUILDFLAG(RTC_USE_H264)
     {"enable-webrtc-h264-with-openh264-ffmpeg",
@@ -1883,8 +1916,7 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_VALUE_TYPE(chrome::android::kImportantSitesInCBD)},
     {"enable-autoplay-muted-videos",
      IDS_FLAGS_ENABLE_AUTOPLAY_MUTED_VIDEOS_NAME,
-     IDS_FLAGS_ENABLE_AUTOPLAY_MUTED_VIDEOS_DESCRIPTION,
-     kOsAndroid,
+     IDS_FLAGS_ENABLE_AUTOPLAY_MUTED_VIDEOS_DESCRIPTION, kOsAndroid,
      SINGLE_VALUE_TYPE(switches::kEnableAutoplayMutedVideos)},
 #endif
     {"enable-pointer-events",  // FLAGS:RECORD_UMA
@@ -1903,15 +1935,13 @@ const FeatureEntry kFeatureEntries[] = {
      IDS_FLAGS_FONT_CACHE_SCALING_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kFontCacheScaling)},
 #if defined(OS_ANDROID)
-    {"enable-vr-shell",
-     IDS_FLAGS_ENABLE_VR_SHELL_NAME,
+    {"enable-vr-shell", IDS_FLAGS_ENABLE_VR_SHELL_NAME,
      IDS_FLAGS_ENABLE_VR_SHELL_DESCRIPTION, kOsAndroid,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableVrShell,
                                switches::kDisableVrShell)},
 #endif
 
-    {"enable-weak-memorycache",
-     IDS_FLAGS_ENABLE_WEAK_MEMORYCACHE_NAME,
+    {"enable-weak-memorycache", IDS_FLAGS_ENABLE_WEAK_MEMORYCACHE_NAME,
      IDS_FLAGS_ENABLE_WEAK_MEMORYCACHE_DESCRIPTION, kOsAll,
      FEATURE_VALUE_TYPE(features::kWeakMemoryCache)},
     // NOTE: Adding new command-line switches requires adding corresponding