Cancel renames in the directory tree when an empty name is chosen.

https://crrev.com/510729 updated renames outside the directory tree;
update renames in the directory tree to match.

Also fix a "Redundant double negation" eslint spotted 40 lines away and
demanded be fixed.

Bug: 934683
Change-Id: I1a915fa4359e87f807ccd0cdc346f3f7b7fba664
Reviewed-on: https://chromium-review.googlesource.com/c/1488478
Commit-Queue: Sam McNally <sammc@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635846}

ui/file_manager/file_manager/foreground/js/directory_tree_naming_controller.js

@@ -91,7 +91,7 @@ DirectoryTreeNamingController.prototype.attachAndStart = function(
   this.isRemovableRoot_ = isRemovableRoot;
   this.volumeInfo_ = this.isRemovableRoot_ ? assert(volumeInfo) : null;
 
-  if (!!this.currentDirectoryItem_) {
+  if (this.currentDirectoryItem_) {
     return;
   }
 
@@ -129,10 +129,8 @@ DirectoryTreeNamingController.prototype.commitRename_ = function() {
   var entry = this.currentDirectoryItem_.entry;
   var newName = this.inputElement_.value;
 
-  // If new name is the same as current name or empty (only for removable
-  // devices), do nothing.
-  if (newName === this.currentDirectoryItem_.label ||
-      (newName.length == 0 && this.isRemovableRoot_)) {
+  // If new name is the same as current name or empty, do nothing.
+  if (newName === this.currentDirectoryItem_.label || newName.length == 0) {
     this.detach_();
     return;
   }

ui/file_manager/integration_tests/file_manager/directory_tree_context_menu.js

@@ -430,8 +430,18 @@ testcase.dirRenameWithoutChangingCurrent = async function() {
 /**
  * Tests renaming a folder to an empty string.
  */
-testcase.dirRenameToEmptyString = function() {
-  return renameDirectoryFromDirectoryTreeAndConfirmAlertDialog('');
+testcase.dirRenameToEmptyString = async function() {
+  const appId = await setupForDirectoryTreeContextMenuTest();
+
+  await remoteCall.navigateWithDirectoryTree(
+      appId, RootPath.DOWNLOADS_PATH + '/photos', 'My files/Downloads');
+  await renamePhotosDirectoryTo(appId, '', false);
+
+  // Wait for the input to be removed.
+  await remoteCall.waitForElementLost(appId, '.tree-row > input');
+
+  // No dialog should be shown.
+  await remoteCall.waitForElementLost(appId, '.cr-dialog-container.shown');
 };
 
 /**