Added Rename Extension Dialog, highlighted renamable title, reorganized dialog management architecture.

> Changed the UI in RenameDialog editTextBox: hightlight and select the renamable
title part of filename, pop-up soft keyboard.
> Added a rename extension dialog if users intend to change extension
part of filename.
> Introduced RenameDialogManager to organize dialog coordinators.

Bug: 924751
Change-Id: If5f4177d03cb4ebaa1faf0a5e5b1ae8ec51de2d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1532917
Commit-Queue: Hesen Zhang <hesen@google.com>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#645989}