[ChromeDriver] Added CommandListener interface

chrome/test/chromedriver/session.h

Index: chrome/test/chromedriver/session.h
diff --git a/chrome/test/chromedriver/session.h b/chrome/test/chromedriver/session.h
index fe837fbf061d252393742ef161326ad3cf8051fe..de01befa090371d847465228163d505cc315242e 100644
--- a/chrome/test/chromedriver/session.h
+++ b/chrome/test/chromedriver/session.h
@@ -16,6 +16,7 @@
 #include "chrome/test/chromedriver/basic_types.h"
 #include "chrome/test/chromedriver/chrome/device_metrics.h"
 #include "chrome/test/chromedriver/chrome/geoposition.h"
+#include "chrome/test/chromedriver/command_listener.h"
 
 namespace base {
 class DictionaryValue;
@@ -36,7 +37,7 @@ struct FrameInfo {
   std::string chromedriver_frame_id;
 };
 
-struct Session {
+struct Session : public CommandListener {

[stgao, 2014/06/15 23:54:40]

Composite pattern might not be good here.
We'd better keep Session as close to a plain object as possible.
How about removing the inheritance of CommandListener here?
You could move logic in Session::OnCommand to
ExecuteSessionCommandOnSessionThread or chrome/test/chromedriver/util.cc/h

   static const base::TimeDelta kDefaultPageLoadTimeout;
 
   explicit Session(const std::string& id);
@@ -44,11 +45,13 @@ struct Session {
   ~Session();
 
   Status GetTargetWindow(WebView** web_view);
+  virtual Status OnCommand(const std::string& command_name) OVERRIDE;
 
   void SwitchToTopFrame();
   void SwitchToParentFrame();
   void SwitchToSubFrame(const std::string& frame_id,
                         const std::string& chromedriver_frame_id);
+  void AddListener(CommandListener* listener);
   std::string GetCurrentFrameId() const;
   std::vector<WebDriverLog*> GetAllLogs() const;
   std::string GetFirstBrowserError() const;
@@ -77,6 +80,7 @@ struct Session {
   base::ScopedTempDir temp_dir;
   scoped_ptr<base::DictionaryValue> capabilities;
   bool auto_reporting_enabled;
+  ScopedVector<CommandListener> command_listeners_;
 };
 
 Session* GetThreadLocalSession();