DevTools: simplify WI.CSSProperty and WI.CSSStyleDeclaration interfaces

LayoutTests/inspector/elements/styles-4/styles-history.html

Index: LayoutTests/inspector/elements/styles-4/styles-history.html
diff --git a/LayoutTests/inspector/elements/styles-4/styles-history.html b/LayoutTests/inspector/elements/styles-4/styles-history.html
index 6a5b111f3cb04d5a3704445989a82eb73d361c74..a6ece5fb0275462ea6e0326e4e267d469e77663d 100644
--- a/LayoutTests/inspector/elements/styles-4/styles-history.html
+++ b/LayoutTests/inspector/elements/styles-4/styles-history.html
@@ -64,7 +64,7 @@ function test()
 
                 function step1(style)
                 {
-                    var property = style.getLiveProperty("margin");
+                    var property = getLiveProperty(style, "margin");
                     property.setText("margin:25px;", false, true).then(dumpHistory(next));
                 }
             },
@@ -75,7 +75,7 @@ function test()
 
                 function step1(style)
                 {
-                    var property = style.getLiveProperty("margin");
+                    var property = getLiveProperty(style, "margin");
                     InspectorTest.addSniffer(WebInspector.UISourceCode.prototype, "addRevision", dumpHistory(next));
                     property.setText("margin:30px;", true, true);
                 }
@@ -124,6 +124,17 @@ function test()
         }
         return result;
     }
+
+    function getLiveProperty(style, name)
+    {
+        for (var property of style.allProperties) {
+            if (!property.activeInStyle())
+                continue;
+            if (property.name === name)
+                return property;
+        }
+        return null;
+    }
 }
 
 </script>