Reify view ownership as a message pipe.

Reify view ownership as a message pipe.

This patch changes the View Manager API to allow for pipelined
creation and addition of views into the view hierarchy using a
new |ViewOwner| object to mediate the transfer of ownership
between clients.

The ownership model ensures that views always belong either to
a view hierarchy (as a child of some other view or as the root
of a view tree) or to a |ViewOwner| in transit.

Previously, it was more difficult to reason about the lifetime
of views since the |ViewToken| afforded no way to track ownership
transfer and therefore lifetime had to be negotiated out-of-band
by applications themselves (a fact which was not adequately captured
by the |ViewProvider| mechanism or example programs).

Bug #654

BUG=
R=abarth@google.com

Committed: https://chromium.googlesource.com/external/mojo/+/83365b19d08baa9ba3f254866a59b01eba496f4f

[jeffbrown, 2016-02-10 01:54:53]

jeffbrown@google.com changed reviewers:
+ abarth@google.com

[abarth, 2016-02-10 04:16:59]

lgtm

[jeffbrown, 2016-02-10 19:08:17]

Description was changed from

==========
Reify view ownership as a message pipe.

This patch changes the View Manager API to allow for pipelined
creation and addition of views into the view hierarchy using a
new |ViewOwner| object to mediate the transfer of ownership
between clients.

The ownership model ensures that views always belong either to
a view hierarchy (as a child of some other view or as the root
of a view tree) or to a |ViewOwner| in transit.

Previously, it was more difficult to reason about the lifetime
of views since the |ViewToken| afforded no way to track ownership
transfer and therefore lifetime had to be negotiated out-of-band
by applications themselves (a fact which was not adequately captured
by the |ViewProvider| mechanism or example programs).

Bug #654

BUG=
==========

to

==========
Reify view ownership as a message pipe.

This patch changes the View Manager API to allow for pipelined
creation and addition of views into the view hierarchy using a
new |ViewOwner| object to mediate the transfer of ownership
between clients.

The ownership model ensures that views always belong either to
a view hierarchy (as a child of some other view or as the root
of a view tree) or to a |ViewOwner| in transit.

Previously, it was more difficult to reason about the lifetime
of views since the |ViewToken| afforded no way to track ownership
transfer and therefore lifetime had to be negotiated out-of-band
by applications themselves (a fact which was not adequately captured
by the |ViewProvider| mechanism or example programs).

Bug #654

BUG=
R=abarth@google.com

Committed:
https://chromium.googlesource.com/external/mojo/+/83365b19d08baa9ba3f254866a5...
==========

[jeffbrown, 2016-02-10 19:08:18]

Committed patchset #2 (id:20001) manually as
83365b19d08baa9ba3f254866a59b01eba496f4f (presubmit successful).