New interface and function for form association

third_party/WebKit/Source/core/html/FormAssociated.h

Index: third_party/WebKit/Source/core/html/FormAssociated.h
diff --git a/third_party/WebKit/Source/core/html/FormAssociated.h b/third_party/WebKit/Source/core/html/FormAssociated.h
new file mode 100644
index 0000000000000000000000000000000000000000..f954ce740a7425a4f4b8aff5b55a9e81d9256df4
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+++ b/third_party/WebKit/Source/core/html/FormAssociated.h
@@ -0,0 +1,20 @@
+// Copyright 2016 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.
+
+#ifndef FormAssociated_h
+#define FormAssociated_h
+
+namespace blink {
+
+class HTMLFormElement;
+
+// Contains code to associate form with a form associated element

[tkent, 2016/12/05 01:53:50]

Please add a specification link.
https://html.spec.whatwg.org/multipage/forms.html#form-associated-element

+class FormAssociated {
+ public:
+  virtual void setAssociatedForm(HTMLFormElement*) = 0;

[tkent, 2016/12/05 01:53:50]

The function name sounds like a simple setter for |m_associatedForm|.  I prefer
something like |associateTo()|.

Can the argument be null?  Please add a comment about it.

+};
+
+}  // namespace blink
+
+#endif  // FormAssociated_h