Add metrics for user manually added exceptions

components/content_settings/core/browser/host_content_settings_map.cc

Index: components/content_settings/core/browser/host_content_settings_map.cc
diff --git a/components/content_settings/core/browser/host_content_settings_map.cc b/components/content_settings/core/browser/host_content_settings_map.cc
index 978aff41c2b478be224d5ca13d801825741151ce..5d1610b532acc45b183236318107359d5e92762f 100644
--- a/components/content_settings/core/browser/host_content_settings_map.cc
+++ b/components/content_settings/core/browser/host_content_settings_map.cc
@@ -10,6 +10,7 @@
 
 #include "base/command_line.h"
 #include "base/macros.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ -168,6 +169,8 @@ HostContentSettingsMap::HostContentSettingsMap(PrefService* prefs,
   content_settings_providers_[DEFAULT_PROVIDER] = default_provider;
 
   MigrateOldSettings();
+
+  CollectExceptionNumberUma();
 }
 
 // static
@@ -487,6 +490,36 @@ void HostContentSettingsMap::MigrateOldSettings() {
   }
 }
 
+void HostContentSettingsMap::CollectExceptionNumberUma() {
+  std::map<ContentSettingsType, std::string> type_info_map;
+  for (const content_settings::ContentSettingsInfo* info :
+       *content_settings::ContentSettingsRegistry::GetInstance())
+    type_info_map[info->website_settings_info()->type()] =
+        info->website_settings_info()->name();

[raymes, 2016/04/14 06:21:59]

I think we can just iterate through WebsiteSettings as we chatted about. Then
you could get rid of the map too.

[lshang, 2016/04/19 02:51:53]

Done.

+
+  for (const content_settings::WebsiteSettingsInfo* info :
+       *content_settings::WebsiteSettingsRegistry::GetInstance())
+    type_info_map[info->type()] = info->name();
+
+  for (const auto& type_info : type_info_map) {
+    ContentSettingsForOneType settings;
+    GetSettingsForOneType(type_info.first, std::string(), &settings);
+    size_t num_exceptions = 0;
+    for (const ContentSettingPatternSource& setting_entry : settings) {
+      if (setting_entry.source == "preference")
+        ++num_exceptions;
+    }
+
+    std::string histogram_name =
+        "ContentSettings.NumberOfExceptions." + type_info.second;
+
+    base::HistogramBase* histogram_pointer = base::Histogram::FactoryGet(
+        histogram_name, 0, 1000, 1001,

[raymes, 2016/04/14 06:21:59]

nit: I think the min should be 1. I'm not sure how many buckets we should have.
1000 might be too many. Maybe 100? Histogram folks will be able to help us. We
need to have granularity at the low levels (e.g. 1, 2, 3, 4, 5) but not at the
high levels (100, 200, 300).

[lshang, 2016/04/19 02:51:53]

Done.
I also changed the name to 'ContentSettings.NumberOfSingleTypeExceptions.'
because there already is a 'NumberOfExceptions' which includes exceptions of all
types.

+        base::HistogramBase::kUmaTargetedHistogramFlag);
+    histogram_pointer->Add(num_exceptions);
+  }
+}
+
 ContentSetting HostContentSettingsMap::GetContentSettingAndMaybeUpdateLastUsage(
     const GURL& primary_url,
     const GURL& secondary_url,