Add ability to find "Internet Search Sites" folder on Mac.

xpcom/io/nsSpecialSystemDirectory.cpp

@@ -315,6 +315,10 @@ void nsSpecialSystemDirectory::operator = (SystemDirectories aSystemSystemDirect
         case Mac_DocumentsDirectory:
             *this = kDocumentsFolderType;
             break;
+
+        case Mac_InternetSearchDirectory:
+            *this = kInternetSearchSitesFolderType;
+            break;
 #endif
             
 #ifdef XP_PC

xpcom/io/nsSpecialSystemDirectory.h

@@ -57,6 +57,7 @@ class NS_COM nsSpecialSystemDirectory : public nsFileSpec
         ,   Mac_FontsDirectory        =   109
         ,   Mac_PreferencesDirectory  =   110
         ,   Mac_DocumentsDirectory    =   111
+        ,   Mac_InternetSearchDirectory    =   112
         
         ,   Win_SystemDirectory       =   201
         ,   Win_WindowsDirectory      =   202