[chrome.displaySource] Session notification improvements

extensions/renderer/display_source_custom_bindings.h

Index: extensions/renderer/display_source_custom_bindings.h
diff --git a/extensions/renderer/display_source_custom_bindings.h b/extensions/renderer/display_source_custom_bindings.h
index 199f199b4663e968a780d31738b54c93f1c704b9..2a6544527df974602d7ed511aab0f1fa0cad20f3 100644
--- a/extensions/renderer/display_source_custom_bindings.h
+++ b/extensions/renderer/display_source_custom_bindings.h
@@ -29,8 +29,12 @@ class DisplaySourceCustomBindings : public ObjectBackedNativeHandler {
       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,
@@ -46,6 +50,16 @@ class DisplaySourceCustomBindings : public ObjectBackedNativeHandler {
   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);