New interface and function for form association

third_party/WebKit/Source/core/html/HTMLImageElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLImageElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLImageElement.cpp b/third_party/WebKit/Source/core/html/HTMLImageElement.cpp
index 01fc2ac62b9849ede2e4d98b0d73447fdedc8672..bd7708e660941c1d7c6fc690c3ccfeec0cc525b1 100644
--- a/third_party/WebKit/Source/core/html/HTMLImageElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLImageElement.cpp
@@ -37,6 +37,7 @@
 #include "core/frame/Deprecation.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/frame/LocalDOMWindow.h"
+#include "core/html/FormAssociated.h"
 #include "core/html/HTMLAnchorElement.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLFormElement.h"
@@ -99,12 +100,6 @@ HTMLImageElement::HTMLImageElement(Document& document,
       m_isFallbackImage(false),
       m_referrerPolicy(ReferrerPolicyDefault) {
   setHasCustomStyleCallbacks();
-  if (form && form->isConnected()) {
-    m_form = form;
-    m_formWasSetByParser = true;
-    m_form->associate(*this);
-    m_form->didAssociateByParser();
-  }
 }
 
 HTMLImageElement* HTMLImageElement::create(Document& document) {
@@ -891,4 +886,13 @@ IntSize HTMLImageElement::bitmapSourceSize() const {
   return IntSize(lSize.width().toInt(), lSize.height().toInt());
 }
 
+void HTMLImageElement::setAssociatedForm(HTMLFormElement* form) {

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

You move the association code to setAssociatedForm() in HTMLImageElement, but
not for HTMLFormControlElement and HTMLObjectElement.  It's inconsistent.

I recommend:
 - Do it for HTMLFormControlElement and HTMLObjectElement too, or
 - Don't add FormAssociated::setAssociatedForm at all in this CL, and introduce
it and update HTMLImageElement, HTMLFormControlElement, and HTMLObjectElement in
a next CL.

+  if (form && form->isConnected()) {
+    m_form = form;
+    m_formWasSetByParser = true;
+    m_form->associate(*this);
+    m_form->didAssociateByParser();
+  }
+};
+
 }  // namespace blink