Remove the ENABLE_IFRAME_SEAMLESS compile-time flag.

Tools/Scripts/webkitperl/FeatureList.pm

 # Copyright (C) 2012 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 # 1.  Redistributions of source code must retain the above copyright
 #     notice, this list of conditions and the following disclaimer.
 # 2.  Redistributions in binary form must reproduce the above copyright
 #     notice, this list of conditions and the following disclaimer in the
@@ skipping 260 matching lines @@
 
     { option => "geolocation", desc => "Toggle Geolocation support",
       define => "ENABLE_GEOLOCATION", default => (isAppleWebKit() || isGtk() || isBlackBerry()), value => \$geolocationSupport },
 
     { option => "high-dpi-canvas", desc => "Toggle High DPI Canvas support",
       define => "ENABLE_HIGH_DPI_CANVAS", default => (isAppleWebKit()), value => \$highDPICanvasSupport },
 
     { option => "icon-database", desc => "Toggle Icondatabase support",
       define => "ENABLE_ICONDATABASE", default => 1, value => \$icondatabaseSupport },
 
-    { option => "iframe-seamless", desc => "Toggle iframe seamless attribute support",
-      define => "ENABLE_IFRAME_SEAMLESS", default => 1, value => \$iframeSeamlessSupport },
-
     { option => "indexed-database", desc => "Toggle Indexed Database support",
       define => "ENABLE_INDEXED_DATABASE", default => isGtk(), value => \$indexedDatabaseSupport },
 
     { option => "input-speech", desc => "Toggle Input Speech support",
       define => "ENABLE_INPUT_SPEECH", default => 0, value => \$inputSpeechSupport },
 
     { option => "input-type-color", desc => "Toggle Input Type Color support",
       define => "ENABLE_INPUT_TYPE_COLOR", default => (isBlackBerry() || isEfl() || isQt()), value => \$inputTypeColorSupport },
 
     { option => "input-type-date", desc => "Toggle Input Type Date support",
@@ skipping 185 matching lines @@
     { option => "xslt", desc => "Toggle XSLT support",
       define => "ENABLE_XSLT", default => 1, value => \$xsltSupport },
 );
 
 sub getFeatureOptionList()
 {
     return @features;
 }
 
 1;