Fix homescreen shortcut targeting on N.
Fix homescreen shortcut targeting on N.

In N if the intent matches the one that triggered your activity,
then the activity will simply be refocused but no additional signals
are given.

This breaks homescreen shortcuts because if you launch Chrome for
the first time via a shortcut, all subsequent launches of the same
shortcut only bring Chrome forward.  They do not create a new tab,
refocus the existing tab, which breaks the experience.

By adding relinquishTaskIdentity to the launcher activity, it is
"forgetting" the triggering intent to the ChromeTabbedActivity and
the task in android is only associated with the intent created and
triggered by ChromeLauncherActivity to create the Tabbed activity.
As this intent is always different from the homescreen shortcuts,
it will ensure that the ChromeTabbedActivity will always get an
onNewIntent for all shortcut pressed.

BUG=606418

Review URL: https://codereview.chromium.org/2100193003 .

Review-Url: https://codereview.chromium.org/2057963003
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#399491}
Cr-Commit-Position: 03d981dee550804c6934fd1a1d9cfa3c172affd3@{#495}
Cr-Branched-From: e9621a186760eb36d74098d9e33e4dd91c427b34@{#394939}

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