CSS style attribute values with semicolons converted to lowercase in IE

[Jeroen]

When pasting this source code into CKEditor (tested with 4.4.4) in Internet Explorer (tested with IE11):

<div style="background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==')">Foo</div>

It is changed into the following code when switching back to the WYSIWYG view:

<div style="background-image: url(&quot;data:image/png;base64,ivborw0kggoaaaansuheugaaaauaaaafcayaaacnbyblaaaaheleqvqi12p4//8/w38giaxdibke0dhxgljnbaao9txl0y4ohwaaaabjru5erkjggg==&quot;);">Foo</div>

Because data URIs are case-sensitive, the image becomes invalid.

The cause is the semicolon before base64. This part of htmldataprocessor.js contains the bug:

if ( CKEDITOR.env.ie ) {
	// IE outputs style attribute in capital letters. We should convert
	// them back to lower case, while not hurting the values (#5930)
	defaultHtmlFilterRulesForAll.attributes.style = function( value, element ) {
		return value.replace( /(^|;)([^\:]+)/g, function( match ) {
			alert(match);
			return match.toLowerCase();
		} );
	};
}

[Jakub Ś]

Problem can be reproduced from CKEditor 4.3 in IE8-11.

[Jakub Ś]

This bug depends on #7352.