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

tools/dom/scripts/systemnative.py

 #!/usr/bin/python
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 """This module provides shared functionality for the systems to generate
 native binding from the IDL database."""
 
 import emitter
 import os
@@ skipping 217 matching lines @@
         arguments,
         self._interface.id,
         'ConstructorRaisesException' in ext_attrs)
 
   def HasSupportCheck(self):
     # Need to omit a support check if it is conditional in JS.
     return self._interface.doc_js_name in js_support_checks
 
   def GetSupportCheck(self):
     # Assume that everything is supported on Dartium.
-    return 'true'
+    value = js_support_checks.get(self._interface.doc_js_name)
+    if type(value) == tuple:
+      return (value[0], 'true')
+    else:
+      return 'true'
 
   def FinishInterface(self):
     self._GenerateCPPHeader()
 
     self._cpp_impl_emitter.Emit(
         self._template_loader.Load('cpp_implementation.template'),
         INTERFACE=self._interface.id,
         INCLUDES=self._GenerateCPPIncludes(self._cpp_impl_includes),
         CALLBACKS=self._cpp_definitions_emitter.Fragments(),
         RESOLVER=self._cpp_resolver_emitter.Fragments(),
@@ skipping 642 matching lines @@
             '    if (Dart_NativeFunction func = $CLASS_NAME::resolver(name, argumentCount))\n'
             '        return func;\n',
             CLASS_NAME=os.path.splitext(os.path.basename(path))[0])
 
 def _IsOptionalStringArgumentInInitEventMethod(interface, operation, argument):
   return (
       interface.id.endswith('Event') and
       operation.id.startswith('init') and
       argument.ext_attrs.get('Optional') == 'DefaultIsUndefined' and
       argument.type.id == 'DOMString')