DevTools: do not assign empty content to CSS UISourceCode in case of protocol error

third_party/WebKit/Source/devtools/front_end/sdk/CSSModel.js

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 34 matching lines @@
       this._resourceTreeModel.addEventListener(
           SDK.ResourceTreeModel.Events.MainFrameNavigated, this._resetStyleSheets, this);
     }
     target.registerCSSDispatcher(new SDK.CSSDispatcher(this));
     this._agent.enable().then(this._wasEnabled.bind(this));
     /** @type {!Map.<string, !SDK.CSSStyleSheetHeader>} */
     this._styleSheetIdToHeader = new Map();
     /** @type {!Map.<string, !Object.<!Protocol.Page.FrameId, !Array.<!Protocol.CSS.StyleSheetId>>>} */
     this._styleSheetIdsForURL = new Map();
 
-    /** @type {!Map.<!SDK.CSSStyleSheetHeader, !Promise<string>>} */
+    /** @type {!Map.<!SDK.CSSStyleSheetHeader, !Promise<?string>>} */
     this._originalStyleSheetText = new Map();
 
     /** @type {!Multimap<string, !Protocol.CSS.StyleSheetId>} */
     this._sourceMapLoadingStyleSheetsIds = new Multimap();
 
     /** @type {!Map<string, !SDK.SourceMap>} */
     this._sourceMapByURL = new Map();
     /** @type {!Multimap<string, !SDK.CSSStyleSheetHeader>} */
     this._sourceMapURLToHeaders = new Multimap();
     Common.moduleSetting('cssSourceMapsEnabled').addChangeListener(this._toggleSourceMapSupport, this);
@@ skipping 711 matching lines @@
   /**
    * @param {!Protocol.CSS.StyleSheetId} styleSheetId
    * @param {!SDK.CSSModel.Edit=} edit
    */
   _fireStyleSheetChanged(styleSheetId, edit) {
     this.dispatchEventToListeners(SDK.CSSModel.Events.StyleSheetChanged, {styleSheetId: styleSheetId, edit: edit});
   }
 
   /**
    * @param {!Protocol.CSS.StyleSheetId} styleSheetId
-   * @return {!Promise<string>}
+   * @return {!Promise<?string>}
    */
   _ensureOriginalStyleSheetText(styleSheetId) {
     var header = this.styleSheetHeaderForId(styleSheetId);
     if (!header)
-      return Promise.resolve('');
+      return Promise.resolve(/** @type {?string} */ (null));
     var promise = this._originalStyleSheetText.get(header);
     if (!promise) {
       promise = this.getStyleSheetText(header.id);
       this._originalStyleSheetText.set(header, promise);
       this._originalContentRequestedForTest(header);
     }
     return promise;
   }
 
   /**
    * @param {!SDK.CSSStyleSheetHeader} header
    */
   _originalContentRequestedForTest(header) {
   }
 
   /**
    * @param {!SDK.CSSStyleSheetHeader} header
-   * @return {!Promise<string>}
+   * @return {!Promise<?string>}
    */
   originalStyleSheetText(header) {
     return this._ensureOriginalStyleSheetText(header.id);
   }
 
   /**
    * @param {!Protocol.CSS.CSSStyleSheetHeader} header
    */
   _styleSheetAdded(header) {
     console.assert(!this._styleSheetIdToHeader.get(header.styleSheetId));
@@ skipping 81 matching lines @@
         return error;
       if (majorChange)
         this._domModel.markUndoableState();
       this._fireStyleSheetChanged(styleSheetId);
       return null;
     }
   }
 
   /**
    * @param {!Protocol.CSS.StyleSheetId} styleSheetId
-   * @return {!Promise<string>}
+   * @return {!Promise<?string>}
    */
   getStyleSheetText(styleSheetId) {
     /**
      * @param {?Protocol.Error} error
      * @param {?string} text
-     * @return {string}
+     * @return {?string}
      */
     function textCallback(error, text) {
       if (error || text === null) {
         console.error('Failed to get text for stylesheet ' + styleSheetId + ': ' + error);
-        text = '';
-        // Fall through.
+        return null;
       }
       return SDK.CSSModel.trimSourceURL(text);
     }
 
-    return this._agent.getStyleSheetText(styleSheetId, textCallback).catchException(/** @type {string} */ (''));
+    return this._agent.getStyleSheetText(styleSheetId, textCallback).catchException(/** @type {?string} */ (null));
   }
 
   _resetStyleSheets() {
     var headers = this._styleSheetIdToHeader.valuesArray();
     this._styleSheetIdsForURL.clear();
     this._styleSheetIdToHeader.clear();
     for (var i = 0; i < headers.length; ++i) {
       this._detachSourceMap(headers[i]);
       this.dispatchEventToListeners(SDK.CSSModel.Events.StyleSheetRemoved, headers[i]);
     }
@@ skipping 227 matching lines @@
 SDK.CSSModel.InlineStyleResult = class {
   /**
    * @param {?SDK.CSSStyleDeclaration} inlineStyle
    * @param {?SDK.CSSStyleDeclaration} attributesStyle
    */
   constructor(inlineStyle, attributesStyle) {
     this.inlineStyle = inlineStyle;
     this.attributesStyle = attributesStyle;
   }
 };