Adding support checks for partially supported element types and updating tests.

sdk/lib/html/scripts/htmldartgenerator.py

Index: sdk/lib/html/scripts/htmldartgenerator.py
diff --git a/sdk/lib/html/scripts/htmldartgenerator.py b/sdk/lib/html/scripts/htmldartgenerator.py
index ff4eb7210c6a95aa13a19284f81b2e532b592e4d..42be19a6758a34c5031646f8ed74f93bcef484b3 100644
--- a/sdk/lib/html/scripts/htmldartgenerator.py
+++ b/sdk/lib/html/scripts/htmldartgenerator.py
@@ -20,6 +20,7 @@ _secure_base_types = {
   'History': 'HistoryBase',
 }
 
+
 class HtmlDartGenerator(object):
   def __init__(self, interface, options):
     self._database = options.database
@@ -28,6 +29,16 @@ class HtmlDartGenerator(object):
     self._interface_type_info = self._type_registry.TypeInfo(self._interface.id)
     self._renamer = options.renamer
 
+  def EmitSupportCheck(self):
+    if self.HasSupportCheck():
+      support_check = self.GetSupportCheck()
+      self._members_emitter.Emit('\n'
+          '  /**\n'
+          '   * Checks if this type is supported on the current platform\n'
+          '   */\n'
+          '  static bool get supported => $SUPPORT_CHECK;\n',
+          SUPPORT_CHECK=support_check)
+
   def EmitAttributeDocumentation(self, attribute):
     """ Emits the MDN dartdoc comment for an attribute.
     """