Write last_modified date to Content Settings in the PrefProvider

components/content_settings/core/browser/host_content_settings_map.h

Index: components/content_settings/core/browser/host_content_settings_map.h
diff --git a/components/content_settings/core/browser/host_content_settings_map.h b/components/content_settings/core/browser/host_content_settings_map.h
index eadf365cfbd2aeea7914d113f75d79a4d1764d29..68a69b6787e21df12f3d5abc98ef29dd65dd85f5 100644
--- a/components/content_settings/core/browser/host_content_settings_map.h
+++ b/components/content_settings/core/browser/host_content_settings_map.h
@@ -48,6 +48,14 @@ class PrefRegistrySyncable;
 class HostContentSettingsMap : public content_settings::Observer,
                                public RefcountedKeyedService {
  public:
+// Whether ContentSettings in the PrefProvider will store a last_modified
+// timestamp.
+#if defined(OS_ANDROID)

[msramek, 2017/04/19 10:49:16]

To answer your question - I'd prefer if this was guarded by our experiment flag.
I trust that you finish this by the next release, but still :) Let's be
conservative.

[dullweber, 2017/04/19 15:02:45]

Done.

+  static const bool kStoreLastModified = true;
+#else
+  static const bool kStoreLastModified = false;
+#endif
+
   enum ProviderType {
     // EXTENSION names is a layering violation when this class will move to
     // components.
@@ -221,9 +229,9 @@ class HostContentSettingsMap : public content_settings::Observer,
   // Otherwise, it only deletes exceptions matched by |pattern_predicate|.
   void ClearSettingsForOneTypeWithPredicate(
       ContentSettingsType content_type,
-      const base::Callback<bool(
-          const ContentSettingsPattern& primary_pattern,
-          const ContentSettingsPattern& secondary_pattern)>& pattern_predicate);
+      const base::Callback<bool(const ContentSettingsPattern& primary_pattern,
+                                const ContentSettingsPattern& secondary_pattern,
+                                base::Time last_modified)>& pattern_predicate);
 
   static bool IsDefaultSettingAllowedForType(ContentSetting setting,
                                              ContentSettingsType content_type);