Drop [ExperimentalCallbackFunction]

third_party/WebKit/Source/bindings/IDLExtendedAttributes.md

Index: third_party/WebKit/Source/bindings/IDLExtendedAttributes.md
diff --git a/third_party/WebKit/Source/bindings/IDLExtendedAttributes.md b/third_party/WebKit/Source/bindings/IDLExtendedAttributes.md
index 834dc81a8f1f6967f2fed23c2d7110eb292e6d0b..feeef1e2e4edc8fd1acfc93ffe497074c34992cd 100644
--- a/third_party/WebKit/Source/bindings/IDLExtendedAttributes.md
+++ b/third_party/WebKit/Source/bindings/IDLExtendedAttributes.md
@@ -20,7 +20,7 @@ Blink IDL also does not support certain recent features of the Web IDL grammar:
 Semantically, only certain extended attributes allow lists. Similarly, only certain extended attributes allow string literals.
 
 Extended attributes either take no value, take a required value, or take an optional value.
-In the following explanations, _(i)_, _(m)_, _(s)_, _(a)_, _(p)_, _(c)_, and _(d)_ mean that a given extended attribute can be specified on interfaces, methods, special operations, attributes, parameters, constants, and dictionaries, respectively. For example, _(a,p)_ means that the IDL attribute can be specified on attributes and parameters.
+In the following explanations, _(i)_, _(m)_, _(s)_, _(a)_, _(p)_, _(c)_, _(d)_, and _(f)_ mean that a given extended attribute can be specified on interfaces, methods, special operations, attributes, parameters, constants, dictionaries, and callback functions respectively. For example, _(a,p)_ means that the IDL attribute can be specified on attributes and parameters.
 
 *** note
 These restrictions are not enforced by the parser: extended attributes used in unsupported contexts will simply be ignored.
@@ -686,7 +686,7 @@ PassRefPtr<XXX> XXX::create(ScriptExecutionContext* context, ScriptState* state,
 
 You can retrieve document or frame from ScriptExecutionContext.
 
-### [Custom] _(i, m, s, a)_
+### [Custom] _(i, m, s, a, f)_
 
 Summary: They allow you to write bindings code manually as you like: full bindings for methods and attributes, certain functions for interfaces.
 
@@ -789,6 +789,19 @@ interface YYY {  // special operations with identifiers
 }
 ```
 
+`[Custom]` may also be specified on callback functions:
+
+```webidl
+[Custom] callback SomeCallback = void ();
+interface XXX {
+    void func(SomeCallback callback);
+};
+```
+
+When`[Custom]` is specified on a callback function, the code generator doesn't
+generate bindings for the callback function. The binding layer uses a
+`ScriptValue` instead.
+
 #### [Custom=PropertyQuery|PropertyEnumerator] _(s)_
 
 Summary: `[Custom=PropertyEnumerator]` allows you to write custom bindings for the case where properties of a given interface are enumerated; a custom named enumerator. There is currently only one use, and in that case it is used with `[Custom=PropertyQuery]`, since the query is also custom.
@@ -1513,10 +1526,6 @@ Without `[NoImplHeader]`, the IDL compiler assumes that there is XXX.h in the im
 
 These extended attributes are _temporary_ and are only in use while some change is in progress. Unless you are involved with the change, you can generally ignore them, and should not use them.
 
-### [ExperimentalCallbackFunction]
-
-Summary: `[ExperimentalCallbackFunction]` on a callback function is a flag to collect callback functions. Currently the code generator doesn't generate bindings for IDL callback functions (instead, it just uses `ScriptValue`). While generating bindings for callback functions, to change existing code which uses callback functions until the generated bindings are stabilized is undesirable. To implement bindings generation for IDL callback functions incrementally, [ExperimentalCallbackFunction] extended attribute is added. The code generator keeps using ScriptValue for IDL callback functions which don't have this extended attribute.
-
 ### [LegacyTreatAsPartialInterface] _(i)_
 
 Summary: `[LegacyTreatAsPartialInterface]` on an interface that is the target of an `implements` statement means that the interface is treated as a partial interface, meaning members are accessed via static member functions in a separate class, rather than as instance methods on the instance object `*impl` or class methods on the C++ class implementing the (main) interface. This is legacy from original implementation of `implements`, and is being removed ([Bug 360435](https://crbug.com/360435), nbarth@).