DevTools: [CSS] migrate setStyleSheetText to promises

LayoutTests/inspector/elements/styles-2/get-set-stylesheet-text.html

Index: LayoutTests/inspector/elements/styles-2/get-set-stylesheet-text.html
diff --git a/LayoutTests/inspector/elements/styles-2/get-set-stylesheet-text.html b/LayoutTests/inspector/elements/styles-2/get-set-stylesheet-text.html
index 8f65813672959beaa58ca80d1e1f6e004f8e9908..e844d855ebcd394d983b35f57ad95545ad80f3d7 100644
--- a/LayoutTests/inspector/elements/styles-2/get-set-stylesheet-text.html
+++ b/LayoutTests/inspector/elements/styles-2/get-set-stylesheet-text.html
@@ -61,7 +61,7 @@ function test()
         InspectorTest.addResult("=== Original stylesheet text: ===");
         InspectorTest.addResult(foundStyleSheetText);
         InspectorTest.cssModel.addEventListener(WebInspector.CSSStyleModel.Events.StyleSheetChanged, next, this);
-        InspectorTest.cssModel.setStyleSheetText(foundStyleSheetHeader.id, "h1 { COLOR: Red; }", true, callback);
+        InspectorTest.cssModel.setStyleSheetText(foundStyleSheetHeader.id, "h1 { COLOR: Red; }", true).then(callback);
     }
 
     function testNewElementStyles()