MAINT-5232: Remove dubious polling in LLMuteList::getInstance().

The LLMuteList singleton instance might be requested before gMessageSystem is
constructed. LLMuteList wants to register a couple gMessageSystem callbacks.
Since gMessageSystem is not (yet) itself an LLSingleton, LLMuteList's
constructor can't just call it into existence. Until now, LLMuteList overrode
LLSingleton's getInstance() method: every time getInstance() was called, the
subclass override method would check whether gMessageSystem had been
initialized, and if so, register its callbacks before forwarding the call to
the base-class LLSingleton::getInstance() method.
Change to use LLPounceable::callWhenReady() instead.
This is the reason gMessageSystem was made an LLPounceable.

indra/newview/llmutelist.cpp

@@ -47,6 +47,7 @@
 #include "pipeline.h"
 
 #include <boost/tokenizer.hpp>
+#include <boost/bind.hpp>
 
 #include "lldispatcher.h"
 #include "llxfermanager.h"
@@ -146,22 +147,6 @@ std::string LLMute::getDisplayType() const
 	}
 }
 
-
-/* static */
-LLMuteList* LLMuteList::getInstance()
-{
-	// Register callbacks at the first time that we find that the message system has been created.
-	static BOOL registered = FALSE;
-	if( !registered && gMessageSystem)
-	{
-		registered = TRUE;
-		// Register our various callbacks
-		gMessageSystem->setHandlerFuncFast(_PREHASH_MuteListUpdate, processMuteListUpdate);
-		gMessageSystem->setHandlerFuncFast(_PREHASH_UseCachedMuteList, processUseCachedMuteList);
-	}
-	return LLSingleton<LLMuteList>::getInstance(); // Call the "base" implementation.
-}
-
 //-----------------------------------------------------------------------------
 // LLMuteList()
 //-----------------------------------------------------------------------------
@@ -169,6 +154,18 @@ LLMuteList::LLMuteList() :
 	mIsLoaded(FALSE)
 {
 	gGenericDispatcher.addHandler("emptymutelist", &sDispatchEmptyMuteList);
+
+	// Register our callbacks. We may be constructed before gMessageSystem, so
+	// use callWhenReady() to register them as soon as gMessageSystem becomes
+	// available.
+	// When using bind(), must be explicit about default arguments such as
+	// that last NULL.
+	gMessageSystem.callWhenReady(boost::bind(&LLMessageSystem::setHandlerFuncFast, _1,
+											 _PREHASH_MuteListUpdate, processMuteListUpdate,
+											 static_cast<void**>(NULL)));
+	gMessageSystem.callWhenReady(boost::bind(&LLMessageSystem::setHandlerFuncFast, _1,
+											 _PREHASH_UseCachedMuteList, processUseCachedMuteList,
+											 static_cast<void**>(NULL)));
 }
 
 //-----------------------------------------------------------------------------

indra/newview/llmutelist.h

@@ -84,11 +84,6 @@ class LLMuteList : public LLSingleton<LLMuteList>
 	LLMuteList();
 	~LLMuteList();
 
-	// Implemented locally so that we can perform some delayed initialization. 
-	// Callers should be careful to call this one and not LLSingleton<LLMuteList>::getInstance()
-	// which would circumvent that mechanism. -MG
-	static LLMuteList* getInstance();
-
 	void addObserver(LLMuteListObserver* observer);
 	void removeObserver(LLMuteListObserver* observer);