DevTools: dedupe source maps when resetting debugging project.

third_party/WebKit/Source/devtools/front_end/bindings/CompilerScriptMapping.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 348 matching lines @@
       var script = this._scriptForSourceMap.get(sourceMap);
       if (!script)
         return;
       for (var sourceURL of sourceMap.sourceURLs()) {
         var uiSourceCode = Bindings.NetworkProject.uiSourceCodeForScriptURL(this._workspace, sourceURL, script);
         if (uiSourceCode)
           this._unbindUISourceCode(uiSourceCode);
       }
     }
 
-    this._sourceMapForURL.valuesArray().forEach(unbindSourceMapSources.bind(this));
+    Array.from(new Set(this._sourceMapForURL.values())).forEach(unbindSourceMapSources.bind(this));
 
     this._sourceMapLoadingPromises.clear();
     this._sourceMapForScriptId.clear();
     this._scriptForSourceMap.clear();
     this._sourceMapForURL.clear();
   }
 
   dispose() {
     Common.EventTarget.removeEventListeners(this._eventListeners);
     this._debuggerReset();
     this._stubProject.dispose();
   }
 };
 
 Bindings.CompilerScriptMapping._originSymbol = Symbol('origin');