Add heuristics to limit showing of new backspace UI bubble.

Add heuristics to limit showing of new backspace UI bubble.

This restricts the bubble to showing 5 times, and only showing when users
trigger backspace twice within three seconds (which likely indicates "hey, why
isn't the browser going back").

The bubble is also immediately hidden (by fading out) if the user successfully
navigates back or forward (by any means) while it's showing.

BUG=610039, 615760
TEST=New "press alt-left to go back" UI should not appear when pressing backspace (to attempt to go back) unless backspace is pressed twice within three seconds.  After the UI is shown 5 times, it should not appear again.
TBR=phajdan.jr

Review-Url: https://codereview.chromium.org/2041293002
Cr-Commit-Position: refs/heads/master@{#399114}
(cherry picked from commit 36aa72944195f579454c1d3abea5045219fd685a)

Committed: https://chromium.googlesource.com/chromium/src/+/6895d9eea0c14482c02bb6b27e756f3fd2abdff2

[Peter Kasting, 2016-06-14 22:35:27]

Description was changed from

==========
Add heuristics to limit showing of new backspace UI bubble.

This restricts the bubble to showing 5 times, and only showing when users
trigger backspace twice within three seconds (which likely indicates "hey, why
isn't the browser going back").

The bubble is also immediately hidden (by fading out) if the user successfully
navigates back or forward (by any means) while it's showing.

BUG=610039,615760
TEST=New "press alt-left to go back" UI should not appear when pressing
backspace (to attempt to go back) unless backspace is pressed twice within three
seconds.  After the UI is shown 5 times, it should not appear again.
TBR=phajdan.jr

Review-Url: https://codereview.chromium.org/2041293002
Cr-Commit-Position: refs/heads/master@{#399114}
(cherry picked from commit 36aa72944195f579454c1d3abea5045219fd685a)
==========

to

==========
Add heuristics to limit showing of new backspace UI bubble.

This restricts the bubble to showing 5 times, and only showing when users
trigger backspace twice within three seconds (which likely indicates "hey, why
isn't the browser going back").

The bubble is also immediately hidden (by fading out) if the user successfully
navigates back or forward (by any means) while it's showing.

BUG=610039,615760
TEST=New "press alt-left to go back" UI should not appear when pressing
backspace (to attempt to go back) unless backspace is pressed twice within three
seconds.  After the UI is shown 5 times, it should not appear again.
TBR=phajdan.jr

Review-Url: https://codereview.chromium.org/2041293002
Cr-Commit-Position: refs/heads/master@{#399114}
(cherry picked from commit 36aa72944195f579454c1d3abea5045219fd685a)

Committed:
https://chromium.googlesource.com/chromium/src/+/6895d9eea0c14482c02bb6b27e75...
==========

[Peter Kasting, 2016-06-14 22:35:29]

Committed patchset #1 (id:1) manually as
6895d9eea0c14482c02bb6b27e756f3fd2abdff2.