[chrome.displaySource] Session notification improvements

extensions/renderer/display_source_custom_bindings.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_RENDERER_DISPLAY_SOURCE_CUSTOM_BINDINGS_H_
 #define EXTENSIONS_RENDERER_DISPLAY_SOURCE_CUSTOM_BINDINGS_H_
 
 #include "base/macros.h"
 #include "extensions/common/api/display_source.h"
 #include "extensions/renderer/api/display_source/display_source_session.h"
@@ skipping 11 matching lines @@
   ~DisplaySourceCustomBindings() override;
 
  private:
   //  ObjectBackedNativeHandler override.
   void Invalidate() override;
 
   void StartSession(
       const v8::FunctionCallbackInfo<v8::Value>& args);
   void TerminateSession(
       const v8::FunctionCallbackInfo<v8::Value>& args);
-
-  void DispatchSessionStarted(int sink_id) const;
+  // Call completion callbacks.
+  enum CallbackType { kStarted, kTerminated };
+  void CallCompletionCallback(int sink_id,
+                              CallbackType type,
+                              const std::string& error_message = "");
+  // Dispatch events
   void DispatchSessionTerminated(int sink_id) const;
   void DispatchSessionError(int sink_id,
                             DisplaySourceErrorType type,
                             const std::string& message) const;
 
   // DisplaySession callbacks.
   void OnSessionStarted(int sink_id);
   void OnSessionTerminated(int sink_id);
   void OnSessionError(int sink_id,
                       DisplaySourceErrorType type,
                       const std::string& message);
 
   DisplaySourceSession* GetDisplaySession(int sink_id) const;
 
   std::map<int, scoped_ptr<DisplaySourceSession>> session_map_;
+  // Data of a call completion callback.
+  struct CallbackInfo {
+    CallbackType type;
+    int sink_id;
+    int call_id;  // Each call has a unique Id.
+  };
+
+  CallbackInfo GetCallbackInfo(CallbackType type, int sink_id) const;
+
+  std::vector<CallbackInfo> callbacks_;
   base::WeakPtrFactory<DisplaySourceCustomBindings> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplaySourceCustomBindings);
 };
 
 }  // extensions
 
 #endif  // EXTENSIONS_RENDERER_DISPLAY_SOURCE_CUSTOM_BINDINGS_H_