Remove a few IDL TODOs that have been fixed in the HTML spec

Source/core/frame/History.idl

Index: Source/core/frame/History.idl
diff --git a/Source/core/frame/History.idl b/Source/core/frame/History.idl
index c8ac612b6d865d08e6f60396641edc57189b2267..0c3ebcf8174cb40734d82ad7625036daabd94ffe 100644
--- a/Source/core/frame/History.idl
+++ b/Source/core/frame/History.idl
@@ -30,13 +30,9 @@ enum ScrollRestoration {"auto", "manual"};
 [
     GarbageCollected,
 ] interface History {
-    // TODO(philipj): length is long in the spec, use that or change the spec:
-    // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28789
     readonly attribute unsigned long length;
     // TODO(philipj): The SerializedScriptValue type should be any.
     [CachedAttribute=stateChanged] readonly attribute SerializedScriptValue state;
-    // TODO(philipj): delta does not have a default value in the spec:
-    // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28790
     [CallWith=ExecutionContext] void go(optional long delta = 0);
     [CallWith=ExecutionContext] void back();
     [CallWith=ExecutionContext] void forward();