GitLab

This is a contingency for the event that the annotation feature is
enabled but form saving is not.
* A new field hasUnsavedChanges is added to the save result, this
  is set when there are edits but form saving is not enabled.
* When this field is true, a dialog is shown to the user allowing
  a choice whether to continue to enter annotation mode or not.
* The annotation toggle event is made custom to avoid re-entrancy
  when entering anntation mode is aborted.

Bug: 902646
Change-Id: I885aa9ee76afb500a086097aed08422ececdf052
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1502255Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dstockwell <dstockwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637893}