Change Chromoting logger to be setup in plugin's NP_Initialize.

remoting/host/plugin/host_script_object.cc

Index: remoting/host/plugin/host_script_object.cc
diff --git a/remoting/host/plugin/host_script_object.cc b/remoting/host/plugin/host_script_object.cc
index 5357cfb65a59e5dc8f04c41ee3bc403709f88eac..da4e9a53f983978a73910afb10c72404af9eda43 100644
--- a/remoting/host/plugin/host_script_object.cc
+++ b/remoting/host/plugin/host_script_object.cc
@@ -72,6 +72,7 @@ const int kMaxLoginAttempts = 5;
 // to the UI. This prevents a potential infinite loop if we encounter an error
 // while sending the log message to the UI.
 static bool g_logging_to_plugin = false;
+static bool g_has_registered_log_handler = false;
 static HostNPScriptObject* g_logging_scriptable_object = NULL;
 static logging::LogMessageHandlerFunction g_logging_old_handler = NULL;
 
@@ -84,17 +85,10 @@ HostNPScriptObject::HostNPScriptObject(NPP plugin, NPObject* parent)
       np_thread_id_(base::PlatformThread::CurrentId()),
       failed_login_attempts_(0),
       disconnected_event_(true, false) {
-  // Set up log message handler.
-  // Note that this approach doesn't quite support having multiple instances
-  // of Chromoting running. In that case, the most recently opened tab will
-  // grab all the debug log messages, and when any Chromoting tab is closed
-  // the logging handler will go away.
-  // Since having multiple Chromoting tabs is not a primary use case, and this
-  // is just debug logging, we're punting improving debug log support for that
-  // case.
-  if (g_logging_old_handler == NULL)
-    g_logging_old_handler = logging::GetLogMessageHandler();
-  logging::SetLogMessageHandler(&LogToUI);
+  // Register this script object as the one that will handle all logging calls
+  // and display them to the user.
+  // If multiple plugins are run, then the last one registered will handle all
+  // logging for all instances.
   g_logging_scriptable_object = this;
 
   VLOG(2) << "HostNPScriptObject";
@@ -109,8 +103,9 @@ HostNPScriptObject::~HostNPScriptObject() {
   // tasks on the UI thread while we are stopping the host.
   desktop_environment_->Shutdown();
 
-  logging::SetLogMessageHandler(g_logging_old_handler);
-  g_logging_old_handler = NULL;
+  // Unregister this script object for logging.
+  // If there are multiple instances and this is the one that was registered
+  // last, then all logging to the UI will be stopped.
   g_logging_scriptable_object = NULL;
 
   // Disconnect synchronously. We cannot disconnect asynchronously
@@ -532,6 +527,33 @@ void HostNPScriptObject::OnStateChanged(State state) {
 }
 
 // static
+void HostNPScriptObject::RegisterLogger() {
+  DCHECK(!g_has_registered_log_handler);
+
+  LOG(INFO) << "Registering global log handler";
+
+  // Record previous handler so we can call it in a chain.
+  g_logging_old_handler = logging::GetLogMessageHandler();
+
+  // Set up log message handler.
+  // Note that this will not log anything until a scriptable object instance
+  // has been created to handle the log message display.
+  logging::SetLogMessageHandler(&LogToUI);
+
+  g_has_registered_log_handler = true;
+}
+
+// static
+void HostNPScriptObject::UnregisterLogger() {
+  // Restore previous handler.
+  logging::SetLogMessageHandler(g_logging_old_handler);
+  g_logging_old_handler = NULL;
+  g_has_registered_log_handler = false;
+
+  LOG(INFO) << "Unregistering global log handler";

[Wez, 2011/08/16 00:05:45]

Why not have these in host_plugin.cc, since that's where they get called from?

[garykac, 2011/08/16 00:19:40]

Because having it here keeps all of the logic (and globals) in one file rather
than having some in the host_plugin and some in the scriptable object.

[Wez, 2011/08/16 00:30:52]

Could they live in their own code file?  The only bit specific to the script
object is the actual call to the logging function.

[garykac, 2011/08/29 23:27:15]

Done.

+}
+
+// static
 bool HostNPScriptObject::LogToUI(int severity, const char* file, int line,
                                  size_t message_start,
                                  const std::string& str) {