DevTools: make CompilerScriptMapping / SASSSourceMapping manage UISourceCodes

third_party/WebKit/Source/devtools/front_end/platform/utilities.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 1074 matching lines @@
 
 /**
  * @return {!Array.<T>}
  * @template T
  */
 Set.prototype.valuesArray = function() {
   return Array.from(this.values());
 };
 
 /**
+ * @return {?T}
+ * @template T
+ */
+Set.prototype.firstValue = function() {
+  if (!this.size)
+    return null;
+  return this.values().next().value;
+};
+
+/**
  * @param {!Iterable<T>|!Array<!T>} iterable
  * @template T
  */
 Set.prototype.addAll = function(iterable) {
   for (var e of iterable)
     this.add(e);
 };
 
 /**
  * @param {!Iterable<T>|!Array<!T>} iterable
@@ skipping 347 matching lines @@
  * @param {function(new:T, ...)} constructorFunction
  * @return {!T}
  */
 function singleton(constructorFunction) {
   if (_singletonSymbol in constructorFunction)
     return constructorFunction[_singletonSymbol];
   var instance = new constructorFunction();
   constructorFunction[_singletonSymbol] = instance;
   return instance;
 }