DevTools: make sure scope variables do not throw exception

third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js

 /*
  * Copyright (C) 2011 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 747 matching lines @@
 
         var fromLine = functionUILocation.lineNumber;
         var fromColumn = functionUILocation.columnNumber;
         var toLine = executionUILocation.lineNumber;
 
         // Make sure we have a chance to update all existing widgets.
         if (this._valueWidgets) {
             for (var line of this._valueWidgets.keys())
                 toLine = Math.max(toLine, line + 1);
         }
-        if (fromLine >= toLine || toLine - fromLine > 500) {
+        if (fromLine >= toLine || toLine - fromLine > 500 || fromLine < 0 || toLine >= this.textEditor.linesCount) {
             this._clearValueWidgets();
             return;
         }
 
         var valuesMap = new Map();
         for (var property of properties)
             valuesMap.set(property.name, property.value);
 
         /** @type {!Map.<number, !Set<string>>} */
         var namesPerLine = new Map();
@@ skipping 350 matching lines @@
         this.uiSourceCode().removeEventListener(WebInspector.UISourceCode.Events.WorkingCopyChanged, this._workingCopyChanged, this);
         this.uiSourceCode().removeEventListener(WebInspector.UISourceCode.Events.WorkingCopyCommitted, this._workingCopyCommitted, this);
         this.uiSourceCode().removeEventListener(WebInspector.UISourceCode.Events.TitleChanged, this._showBlackboxInfobarIfNeeded, this);
         WebInspector.moduleSetting("skipStackFramesPattern").removeChangeListener(this._showBlackboxInfobarIfNeeded, this);
         WebInspector.moduleSetting("skipContentScripts").removeChangeListener(this._showBlackboxInfobarIfNeeded, this);
         WebInspector.UISourceCodeFrame.prototype.dispose.call(this);
     },
 
     __proto__: WebInspector.UISourceCodeFrame.prototype
 }