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

sdk/lib/html/scripts/systemnative.py

Index: sdk/lib/html/scripts/systemnative.py
diff --git a/sdk/lib/html/scripts/systemnative.py b/sdk/lib/html/scripts/systemnative.py
index 3b20eab4e600a51dcdf8f0aa6fc05c09e33cb857..508d9c672e4b67b2633c4e349c2995c47779b3bc 100644
--- a/sdk/lib/html/scripts/systemnative.py
+++ b/sdk/lib/html/scripts/systemnative.py
@@ -10,6 +10,7 @@ import emitter
 import os
 from generator import *
 from htmldartgenerator import *
+from systemhtml import js_support_checks
 
 class DartiumBackend(HtmlDartGenerator):
   """Generates Dart implementation for one DOM IDL interface."""
@@ -200,6 +201,14 @@ class DartiumBackend(HtmlDartGenerator):
         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'
+
   def FinishInterface(self):
     self._GenerateCPPHeader()