Content Settings: Add RevocationObserver to measure when permissions are revoked

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 d1151eab85af2a51fa622b979cda1d05674ff2a3..1c5390b55df20616146439b1d3a3bbf20beb1b6d 100644
--- a/components/content_settings/core/browser/host_content_settings_map.cc
+++ b/components/content_settings/core/browser/host_content_settings_map.cc
@@ -453,6 +453,9 @@ void HostContentSettingsMap::SetContentSettingDefaultScope(
           content_type);
   DCHECK(info);
 
+  ContentSetting previous_value = GetContentSetting(
+      primary_url, secondary_url, content_type, resource_identifier);
+
   content_settings::PatternPair patterns =
       GetPatternsFromScopingType(info->website_settings_info()->scoping_type(),
                                  primary_url, secondary_url);
@@ -463,6 +466,19 @@ void HostContentSettingsMap::SetContentSettingDefaultScope(
 
   SetContentSetting(primary_pattern, secondary_pattern, content_type,
                     resource_identifier, setting);
+
+  ContentSetting final_value = GetContentSetting(
+      primary_url, secondary_url, content_type, resource_identifier);
+
+  if (previous_value == CONTENT_SETTING_ALLOW &&
+      final_value != CONTENT_SETTING_ALLOW) {
+    FOR_EACH_OBSERVER(content_settings::Observer,
+                      observers_,
+                      OnContentSettingRevoked(primary_url,
+                                              secondary_url,
+                                              content_type,
+                                              resource_identifier));
+  }
 }
 
 ContentSetting HostContentSettingsMap::GetContentSettingAndMaybeUpdateLastUsage(