No ticket. Abstract conditional hook definition.

src/css/addGetHookIf.js

@@ -0,0 +1,33 @@
+define( function() {
+
+function addGetHookIf( hookVar, conditionFn, hookFn ) {
+	// Define the hook, we'll check on the first run if it's really needed.
+	hookVar = {
+		get: function() {
+			var condition = conditionFn();
+
+			if ( condition == null ) {
+				// The test was not ready at this point; screw the hook this time
+				// but check again when needed next time.
+				return;
+			}
+
+			if ( condition ) {
+				// Hook not needed (or it's not possible to use it due to missing dependency),
+				// remove it.
+				// Since there are no other hooks for marginRight, remove the whole object.
+				delete hookVar.get;
+				return;
+			}
+
+			// Hook needed; redefine it so that the support test is not executed again.
+			hookVar.get = hookFn;
+
+			return hookVar.get.apply( hookVar, arguments );
+		}
+	};
+}
+
+return addGetHookIf;
+
+});