[WIP] bindings: Introduce PropertyBag

Source/bindings/scripts/idl_types.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """IDL type handling.
 
 Classes:
 IdlTypeBase
  IdlType
  IdlUnionType
  IdlArrayOrSequenceType
@@ skipping 181 matching lines @@
                    self.name == 'Object' or
                    self.name == 'Promise')  # Promise will be basic in future
 
     @property
     def is_string_type(self):
         return self.name in STRING_TYPES
 
     @property
     def may_raise_exception_on_conversion(self):
         return (self.is_integer_type or
+                self.is_dictionary or
                 self.name in ('ByteString', 'ScalarValueString'))
 
     @property
     def is_union_type(self):
         return isinstance(self, IdlUnionType)
 
     @property
     def name(self):
         """Return type name
 
@@ skipping 117 matching lines @@
     def is_nullable(self):
         return True
 
     @property
     def name(self):
         return self.inner_type.name + 'OrNull'
 
     def resolve_typedefs(self, typedefs):
         self.inner_type = self.inner_type.resolve_typedefs(typedefs)
         return self