DevTools: dedupe source maps when resetting debugging project.

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

Index: third_party/WebKit/Source/devtools/front_end/bindings/CompilerScriptMapping.js
diff --git a/third_party/WebKit/Source/devtools/front_end/bindings/CompilerScriptMapping.js b/third_party/WebKit/Source/devtools/front_end/bindings/CompilerScriptMapping.js
index 8a4b5259434ed8b93f4f40b540fe3c995bb5e95c..320eb1cdb6e1a25c65381d381dfaaee1c8139041 100644
--- a/third_party/WebKit/Source/devtools/front_end/bindings/CompilerScriptMapping.js
+++ b/third_party/WebKit/Source/devtools/front_end/bindings/CompilerScriptMapping.js
@@ -366,7 +366,7 @@ Bindings.CompilerScriptMapping = class {
       }
     }
 
-    this._sourceMapForURL.valuesArray().forEach(unbindSourceMapSources.bind(this));
+    Array.from(new Set(this._sourceMapForURL.values())).forEach(unbindSourceMapSources.bind(this));
 
     this._sourceMapLoadingPromises.clear();
     this._sourceMapForScriptId.clear();