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Procedure of App returning to foreground:
1. applicationWillEnterForeground (normal App event)
2. performActionForShortcutItem (3d-touch event like 'open new tab')
3. applicationDidBecomeActive (normal App event)

Current impl judges if an NTP should be opened in step1, and create that NTP
in step3. Step2 also creates an NTP because no one exists after step1.

Bug: 831124
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Ib77cabca10b4afdfd01cd0ade20a7ea254f04188
Reviewed-on: https://chromium-review.googlesource.com/1172689
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582926}