Implement RevokePermission() method in PermissionService.

content/public/browser/content_browser_client.h

Index: content/public/browser/content_browser_client.h
diff --git a/content/public/browser/content_browser_client.h b/content/public/browser/content_browser_client.h
index 627353d23f3a4e9f054fdae4cb5b3bae1b85fd3a..54f282dc5ceb216fa4806e4885b5fced7385d6e8 100644
--- a/content/public/browser/content_browser_client.h
+++ b/content/public/browser/content_browser_client.h
@@ -445,6 +445,12 @@ class CONTENT_EXPORT ContentBrowserClient {
       const GURL& requesting_origin,
       const GURL& embedding_origin);
 
+  virtual PermissionStatus RevokePermission(
+      PermissionType permission,
+      BrowserContext* browser_context,
+      const GURL& requesting_origin,
+      const GURL& embedding_origin);
+
   // Returns true if the given page is allowed to open a window of the given
   // type. If true is returned, |no_javascript_access| will indicate whether
   // the window that is created should be scriptable/in the same process.