Convert the inspector framework to use ES6 classes.

sky/framework/inspector/css-agent.sky

 <script>
-function CSS(domAgent) {
-  this.domAgent_ = domAgent;
-}
+class CSS {
+  constructor(domAgent) {
+    this.domAgent_ = domAgent;
+    Object.preventExtensions(this);
+  }
 
-CSS.prototype.enable = function() {
-};
+  enable() {
+  }
 
-CSS.prototype.getInlineStylesForNode = function(params) {
-  return {
+  getInlineStylesForNode(params) {
+    return {
       "inlineStyle": {
-      "cssProperties": [],
-      "shorthandEntries": [],
-      "styleSheetId": "0",
-      "range": {
-        "startLine": 0,
-        "startColumn": 0,
-        "endLine": 0,
-        "endColumn": 0
-      },
-      "cssText": "",
+        "cssProperties": [],
+        "shorthandEntries": [],
+        "styleSheetId": "0",
+        "range": {
+          "startLine": 0,
+          "startColumn": 0,
+          "endLine": 0,
+          "endColumn": 0
+        },
+        "cssText": "",
+      }
+    };
+  }
+
+  getComputedStyleForNode(params) {
+    var node = this.domAgent_.getNodeForId(params.nodeId);
+    if (!node){
+      console.log("Error, missing node" + params.nodeId);
+      return { "computedStyle": [] };
     }
+    var style = window.getComputedStyle(node, null);
+    if (!style){
+      console.log("Error, no computed style for " + params.nodeId + " " + node);
+      return { "computedStyle": [] };
+    }
+    var computedStyles = [];
+    for (var i = 0; i < style.length; i++) {
+      var name = style.item(i);
+      computedStyles.push({
+        "name": name,
+        "value": style.getPropertyValue(name),
+      });
+    }
+    return {
+      "computedStyle": computedStyles,
+    };
   }
 }
 
-CSS.prototype.getComputedStyleForNode = function(params) {
-  var node = this.domAgent_.getNodeForId(params.nodeId);
-  if (!node){
-    console.log("Error, missing node" + params.nodeId);
-    return { "computedStyle": [] };
-  }
-  var style = window.getComputedStyle(node, null);
-  if (!style){
-    console.log("Error, no computed style for " + params.nodeId + " " + node);
-    return { "computedStyle": [] };
-  }
-  var computedStyles = [];
-  for (var i = 0; i < style.length; i++) {
-    var name = style.item(i);
-    computedStyles.push({
-      "name": name,
-      "value": style.getPropertyValue(name),
-    });
-  }
-  return {
-    "computedStyle": computedStyles,
-  }
-}
-
 module.exports = CSS;
 </script>