Content Settings: Add RevocationObserver to measure when permissions are revoked

components/content_settings/core/browser/content_settings_observer.h

Index: components/content_settings/core/browser/content_settings_observer.h
diff --git a/components/content_settings/core/browser/content_settings_observer.h b/components/content_settings/core/browser/content_settings_observer.h
index 41868578942081c5020c86846319318f367aa47d..2a408c2d42ff857d0082c7bb0c0d89fc272fa938 100644
--- a/components/content_settings/core/browser/content_settings_observer.h
+++ b/components/content_settings/core/browser/content_settings_observer.h
@@ -20,6 +20,12 @@ class Observer {
       ContentSettingsType content_type,
       std::string resource_identifier) = 0;
 
+  virtual void OnContentSettingRevoked(

[raymes, 2016/03/21 01:52:56]

nit: perhaps add a comment about when this is called? Specifically it's only
fired if a content setting goes from ALLOW to something else when the user's
preference for a particular origin is changed (via
SetContentSettingDefaultScope)

[tsergeant, 2016/03/21 03:38:38]

Done.

+      const GURL& primary_url,
+      const GURL& secondary_url,
+      ContentSettingsType content_type,
+      std::string resource_identifier) {};
+
  protected:
   virtual ~Observer() {}
 };