[DevTools] Refactor CSS live locations.

third_party/WebKit/Source/devtools/front_end/bindings/StylesSourceMapping.js

 /*
  * Copyright (C) 2012 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 45 matching lines @@
       SDK.ResourceTreeModel.fromTarget(cssModel.target())
           .addEventListener(SDK.ResourceTreeModel.Events.MainFrameNavigated, this._unbindAllUISourceCodes, this)
     ];
   }
 
   /**
    * @param {!SDK.CSSLocation} rawLocation
    * @return {?Workspace.UILocation}
    */
   rawLocationToUILocation(rawLocation) {
-    var uiSourceCode =
-        Bindings.NetworkProject.uiSourceCodeForStyleURL(this._workspace, rawLocation.url, rawLocation.header());
+    var header = rawLocation.header();
+    if (!header)
+      return null;
+    var uiSourceCode = Bindings.NetworkProject.uiSourceCodeForStyleURL(this._workspace, rawLocation.url, header);
     if (!uiSourceCode)
       return null;
     var lineNumber = rawLocation.lineNumber;
     var columnNumber = rawLocation.columnNumber;
-    var header = this._cssModel.styleSheetHeaderForId(rawLocation.styleSheetId);
     if (header && header.isInline && header.hasSourceURL) {
       lineNumber -= header.lineNumberInSource(0);
       columnNumber -= header.columnNumberInSource(lineNumber, 0);
     }
     return uiSourceCode.uiLocation(lineNumber, columnNumber);
   }
 
   /**
    * @param {!Common.Event} event
    */
@@ skipping 269 matching lines @@
 
   dispose() {
     if (this._terminated)
       return;
     this._terminated = true;
     Common.EventTarget.removeEventListeners(this._eventListeners);
   }
 };
 
 Bindings.StyleFile.updateTimeout = 200;