Add white color variant of checkmark icon

core/css/icons.css

@@ -47,6 +47,10 @@
 	background-image: url('../img/actions/checkmark.svg');
 }
 
+.icon-checkmark-white {
+	background-image: url('../img/actions/checkmark-white.svg');
+}
+
 .icon-clock {
 	background-image: url('../img/actions/clock.svg');
 }

core/img/actions/checkmark-white.svg

@@ -0,0 +1,4 @@
+<svg xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://www.w3.org/2000/svg" version="1.1" xml:space="preserve" height="16px" viewBox="-0.5 -0.5 16 16" width="16px" enable-background="new -0.5 -0.5 16 16" y="0px" x="0px" xmlns:cc="http://creativecommons.org/ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" overflow="visible"><metadata><rdf:RDF><cc:Work rdf:about=""><dc:format>image/svg+xml</dc:format><dc:type rdf:resource="http://purl.org/dc/dcmitype/StillImage"/><dc:title/></cc:Work></rdf:RDF></metadata><defs>
+</defs>
+<path fill="#ffffff" d="M12.438,3.6875c-0.363,0-0.726,0.1314-1,0.4063l-4.5005,4.5-1.9687-2c-0.5498-0.5484-1.4489-0.5498-2,0l-0.5,0.5c-0.5512,0.5496-0.5512,1.4502,0,2l2.9687,2.9682c0.0063,0.007-0.0065,0.025,0,0.032l0.5,0.5c0.5497,0.55,1.4503,0.55,2,0l0.5-0.5,0.1875-0.219,5.313-5.2812c0.549-0.5498,0.549-1.4503,0-2l-0.5-0.5c-0.275-0.2749-0.638-0.4063-1-0.4063z" transform="translate(-0.5,-0.5)"/>
+</svg>