Support nullable attributes and return types in Dartium.

tools/dom/idl/dart/dart.idl

Index: tools/dom/idl/dart/dart.idl
diff --git a/tools/dom/idl/dart/dart.idl b/tools/dom/idl/dart/dart.idl
index fddff5b5ff51792c036d17c64f4f95a2fe79c9e9..0b1745700991a4f21b75923e8b30d626086311cd 100644
--- a/tools/dom/idl/dart/dart.idl
+++ b/tools/dom/idl/dart/dart.idl
@@ -42,16 +42,6 @@ interface Console {
   [CallWith=ScriptArguments|ScriptState] void assertCondition(boolean condition);
 };
 
-// TODO(antonm): remove those overrides and corresponding custom methods.
-[Supplemental]
-interface Coordinates {
-    [Custom] readonly attribute double altitude;
-    [Custom] readonly attribute double altitudeAccuracy;
-    [Custom] readonly attribute double heading;
-    [Custom] readonly attribute double speed;
-};
-
-
 interface HTMLCanvasElement {
   [Suppressed] DOMString toDataURL([TreatNullAs=NullString, TreatUndefinedAs=NullString,Optional=DefaultIsUndefined] in DOMString type) raises(DOMException);
   [Custom] DOMString toDataURL([TreatNullAs=NullString, TreatUndefinedAs=NullString,Optional=DefaultIsUndefined] in DOMString type, [Optional] in float quality) raises(DOMException);