Add supported checks to the SVG library, and library cleanup.

tools/dom/scripts/htmldartgenerator.py

Index: tools/dom/scripts/htmldartgenerator.py
diff --git a/tools/dom/scripts/htmldartgenerator.py b/tools/dom/scripts/htmldartgenerator.py
index 5d18f07d233e31746db7316654a9c53ddf39ecc7..20b7d936eca84a15201d97d881d6af4c4a4f2fa7 100644
--- a/tools/dom/scripts/htmldartgenerator.py
+++ b/tools/dom/scripts/htmldartgenerator.py
@@ -32,11 +32,16 @@ class HtmlDartGenerator(object):
 
   def EmitSupportCheck(self):
     if self.HasSupportCheck():
-      support_check = self.GetSupportCheck()
+      check = self.GetSupportCheck()
+      if type(check) != tuple:
+        signature = 'get supported'
+      else:
+        signature = check[0]
+        check = check[1]
       self._members_emitter.Emit('\n'
           '  /// Checks if this type is supported on the current platform.\n'
-          '  static bool get supported => $SUPPORT_CHECK;\n',
-          SUPPORT_CHECK=support_check)
+          '  static bool $SIGNATURE => $SUPPORT_CHECK;\n',
+          SIGNATURE=signature, SUPPORT_CHECK=check)
 
   def EmitEventGetter(self, events_class_name):
     self._members_emitter.Emit(