Make permission dialogs tab-modal

This change addresses issue where permission dialog stays visible after
javastript code on the page opened different origin in a new tab.

After switching to tab-modal dialog, navigation in different tab will
cause ModalDialogManager to dismiss currently opened dialog.

BUG=945067
R=huayinz@chromium.org

Change-Id: I942f8163087b4a6e952a635f48833203256d184e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1565445
Reviewed-by: Becky Zhou <huayinz@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Pavel Yatsuk <pavely@chromium.org>
Cr-Commit-Position: refs/heads/master@{#651085}