Add support for log file rotation.

ui/file_manager/file_manager/common/js/mock_entry.js

Index: ui/file_manager/file_manager/common/js/mock_entry.js
diff --git a/ui/file_manager/file_manager/common/js/mock_entry.js b/ui/file_manager/file_manager/common/js/mock_entry.js
index 26b9541daed4494141740ac56167db226b46da77..7f3515529380cb33e0652ba7f3bf13b0f86d1c67 100644
--- a/ui/file_manager/file_manager/common/js/mock_entry.js
+++ b/ui/file_manager/file_manager/common/js/mock_entry.js
@@ -91,6 +91,7 @@ function MockEntry(filesystem, fullPath) {
   filesystem.entries[fullPath] = this;
   this.filesystem = filesystem;
   this.fullPath = fullPath;
+  this.removed_ = false;
 }
 
 MockEntry.prototype = {
@@ -168,12 +169,20 @@ MockEntry.prototype.copyTo =
  * @param {function(Object)} onError Callback invoked with an error object.
  */
 MockEntry.prototype.remove = function(onSuccess, onError) {
+  this.removed_ = true;
   Promise.resolve().then(function() {
     this.filesystem.entries[this.fullPath] = null;
   }.bind(this)).then(onSuccess, onError);
 };
 
 /**
+ * Asserts that the entry was removed.
+ */
+MockEntry.prototype.assertRemoved = function() {
+  assertTrue(this.removed_);
+};
+
+/**
  * Clones the entry with the new fullpath.
  *
  * @param {string} fullpath New fullpath.