Bug 285963 – Remove composite attribute on HTMLImageElement

• Component: Images
• Status: RESOLVED FIXED

[Karl Dubost]

https://searchfox.org/wubkat/rev/19fb3bc3aa27a28183dbc388d1ba5df1cbb2feb6/Source/WebCore/html/HTMLImageElement.cpp#400-406
```cpp
case AttributeNames::compositeAttr: {
    // FIXME: images don't support blend modes in their compositing attribute.
    BlendMode blendOp = BlendMode::Normal;
    if (!parseCompositeAndBlendOperator(newValue, m_compositeOperator, blendOp))
        m_compositeOperator = CompositeOperator::SourceOver;
    break;
}
```

This was added on Apr 27, 2004 (thanks Simon Fraser for the archeology)
https://commits.webkit.org/5738@main

```
WebKit:
	Added support for specifying composite operation on an
	image element, i.e.:

	<img composite="source-over" src="triangle.png">
	<img style="position:relative; left:-200px;" composite="destination-in" src="circle.png">

	This feature was requested by the dashboard guys.  They can use it to apply
	transparency masks to widgies.
```

Which means it could probably be removed.

[Radar WebKit Bug Importer]

<rdar://problem/143109250>

[Karl Dubost]

Pull request: https://github.com/WebKit/WebKit/pull/39182

[EWS]

Committed 289071@main (7c0fc80dff6b): <https://commits.webkit.org/289071@main>

Reviewed commits have been landed. Closing PR #39182 and removing active labels.