Re-implement cancellation of copyFileEntry_().

chrome/browser/resources/file_manager/js/util.js

Index: chrome/browser/resources/file_manager/js/util.js
diff --git a/chrome/browser/resources/file_manager/js/util.js b/chrome/browser/resources/file_manager/js/util.js
index aa1351634deb8c81d5fd134da00cc24b50ba17e7..2023266cf86bde7f234c7bf59a958c91303f3e2c 100644
--- a/chrome/browser/resources/file_manager/js/util.js
+++ b/chrome/browser/resources/file_manager/js/util.js
@@ -505,11 +505,7 @@ util.deduplicatePath = function(dirEntry, relativePath, onSuccess, onError) {
       // Hit the limit of the number of retrial.
       // Note that we cannot create FileError object directly, so here we use
       // Object.create instead.
-      onError(Object.create(FileError.prototype, {
-        code: {
-          get: function() { return FileError.PATH_EXISTS_ERR; }
-        }
-      }));
+      onError(util.createFileError(FileError.PATH_EXISTS_ERR));
       return;
     }
 
@@ -1167,3 +1163,16 @@ util.isFakeDirectoryEntry = function(entry) {
   // Currently, fake entry doesn't support createReader.
   return !('createReader' in entry);
 };
+
+/**
+ * Creates a FileError instance with given code.
+ * Note that we cannot create FileError instance by "new FileError(code)",
+ * unfortunately, so here we use Object.create.
+ * @param {number} code Error code for the FileError.
+ * @return {FileError} FileError instance
+ */
+util.createFileError = function(code) {
+  return Object.create(FileError.prototype, {
+    code: { get: function() { return code; } }
+  });
+};