coral: change the way to get app ID

This cl changes the way of getting app ID by directly getting the ID
from the kAppIDKey such that the PWAs can have unique App IDs.

Tested that the Arc Apps also have unique IDs.

Test: manually test for Arc + browser test
Bug: b:369681496
Change-Id: Iace78964f99b5c8ffc06fa4b41662e16d7b716dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5892202
Commit-Queue: Xiaodan Zhu <zxdan@chromium.org>
Reviewed-by: Matthew Mourgos <mmourgos@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1360290}