LayoutTestPermissionManager: implement subscriptions handling.

content/shell/browser/layout_test/layout_test_permission_manager.h

Index: content/shell/browser/layout_test/layout_test_permission_manager.h
diff --git a/content/shell/browser/layout_test/layout_test_permission_manager.h b/content/shell/browser/layout_test/layout_test_permission_manager.h
index 9c0461f7788d6aa3f6a8a70f9a36408dd6ba40cc..8aa905e23623267b365aaeda0f08d3e7b9b4fd92 100644
--- a/content/shell/browser/layout_test/layout_test_permission_manager.h
+++ b/content/shell/browser/layout_test/layout_test_permission_manager.h
@@ -7,6 +7,7 @@
 
 #include "base/callback_forward.h"
 #include "base/containers/hash_tables.h"
+#include "base/id_map.h"
 #include "base/macros.h"
 #include "base/synchronization/lock.h"
 #include "content/public/browser/permission_manager.h"
@@ -56,10 +57,12 @@ class LayoutTestPermissionManager : public PermissionManager {
  private:
   // Representation of a permission for the LayoutTestPermissionManager.
   struct PermissionDescription {
+    PermissionDescription() = default;
     PermissionDescription(PermissionType type,
                           const GURL& origin,
                           const GURL& embedding_origin);
     bool operator==(const PermissionDescription& other) const;
+    bool operator!=(const PermissionDescription& other) const;
 
     // Hash operator for hash maps.
     struct Hash {
@@ -71,10 +74,15 @@ class LayoutTestPermissionManager : public PermissionManager {
     GURL embedding_origin;
   };
 
+  struct Subscription;
+  using SubscriptionsMap = IDMap<Subscription, IDMapOwnPointer>;
   using PermissionsMap = base::hash_map<PermissionDescription,
                                         PermissionStatus,
                                         PermissionDescription::Hash>;
 
+  void OnPermissionChanged(const PermissionDescription& permission,
+                           PermissionStatus status);
+
   // Mutex for permissions access. Unfortunately, the permissions can be
   // accessed from the IO thread because of Notifications' synchronous IPC.
   base::Lock permissions_lock_;
@@ -83,6 +91,9 @@ class LayoutTestPermissionManager : public PermissionManager {
   // their associated |PermissionStatus|.
   PermissionsMap permissions_;
 
+  // List of subscribers currently listening to permission changes.
+  SubscriptionsMap subscriptions_;
+
   DISALLOW_COPY_AND_ASSIGN(LayoutTestPermissionManager);
 };