Drop raises annotations support.

tools/dom/scripts/systemnative.py

Index: tools/dom/scripts/systemnative.py
diff --git a/tools/dom/scripts/systemnative.py b/tools/dom/scripts/systemnative.py
index 698205b72670aaa69324d59799f1cffd4ec3ab7a..a8672db99c0f572f232153b1621fa0441baa0b73 100644
--- a/tools/dom/scripts/systemnative.py
+++ b/tools/dom/scripts/systemnative.py
@@ -357,7 +357,7 @@ class DartiumBackend(HtmlDartGenerator):
         [],
         attr.type.id,
         attr.type.nullable,
-        attr.get_raises or 'GetterRaisesException' in attr.ext_attrs)
+        'GetterRaisesException' in attr.ext_attrs)
 
   def _AddSetter(self, attr, html_name):
     type_info = self._TypeInfo(attr.type.id)
@@ -387,7 +387,7 @@ class DartiumBackend(HtmlDartGenerator):
         [attr],
         'void',
         False,
-        attr.set_raises or 'SetterRaisesException' in attr.ext_attrs)
+        'SetterRaisesException' in attr.ext_attrs)
 
   def AddIndexer(self, element_type):
     """Adds all the methods required to complete implementation of List."""
@@ -531,7 +531,7 @@ class DartiumBackend(HtmlDartGenerator):
         arguments,
         operation.type.id,
         operation.type.nullable,
-        operation.raises or 'RaisesException' in operation.ext_attrs)
+        'RaisesException' in operation.ext_attrs)
 
   def _GenerateNativeCallback(self,
       callback_name,