[regression] Multi-finger gestures are often not detected as finished (Mir reports one finger still down after all are released)

See also bug 1480654.

Dropped to medium. It appears this regression is also partly due to faulty gesture logic introduced in:

------------------------------------------------------------
revno: 2564 [merge]
author: Robert Carr <email address hidden>
committer: Tarmac
branch nick: development-branch
timestamp: Mon 2015-05-11 20:13:20 +0000
message:
  Port playground window manager to event 2.0.

  Approved by Alan Griffiths, PS Jenkins bot, Alexandros Frantzis, Kevin DuBois.
------------------------------------------------------------

So this regression only affects mir_proving_server. Still, we need to fix it to have a stable testbed to work on bug 1480654.

Even after fixing the regression of r2564 this bug persists. Some simple logging shows the remaining issue introduced in r2591:

Here I swipe 4 fingers and release them all:

4 touches, 0 released
4 touches, 1 released
3 touches, 0 released
3 touches, 0 released
3 touches, 1 released
2 touches, 0 released
2 touches, 1 released
1 touches, 0 released

See how Mir thinks one finger was never released. That's the bug.

Fix committed into lp:mir at revision None, scheduled for release in mir, milestone 0.16.0

This bug was fixed in the package mir - 0.15.0+15.10.20150818-0ubuntu1

---------------
mir (0.15.0+15.10.20150818-0ubuntu1) wily; urgency=medium

  [ Daniel van Vugt ]
  * New upstream release 0.15.0 (https://launchpad.net/mir/+milestone/0.15.0)
    - ABI summary: Only servers and graphics drivers need rebuilding;
      . Mirclient ABI unchanged at 9
      . Mirserver ABI bumped to 33
      . Mircommon ABI unchanged at 5
      . Mirplatform ABI bumped to 9
    - Enhancements:
      . Add support for Mir-on-X11.
      . Latency reduction optimizations (around ~15ms reduction in total):
        Reduced input event resampling latency by 5ms. Reduced output latency
        (in system compositors) by around 10ms with the introduction of
        "predictive bypass". And we're not finished; future Mir releases
        should reduce latency further.
      . Introduced a python3-based Mir performance framework.
      . Lots of preparation for an architectural overhaul of buffer swapping,
        required in the least to support future optimizations like nested
        bypass.
      . Added a new cursor: crosshair
      . Added support for 15/16-bit client pixel formats ("high colour").
      . Added a new client function to make picking the right pixel format
        for a given EGLConfig super simple: mir_connection_get_egl_pixel_format
      . Added application-not-responding detection
      . Added client API for specifying input region shape.
      . Fixed the remaining threading flaws identified by ThreadSanitizer and
        turned it on permanently for all continuous integration in future.
      . Added support for relative pointer motion events (e.g. for gaming).
    - Bug fixes:
      . Fix focus issues breaking autopilot tests entering text (LP: #1468029)
      . Fix mir tests failure on armhf with GCC5 (LP: #1478213)
      . mir_buffer_stream_swap_buffers_sync can hang constraints (LP: #1479899)
      . Loading libmirclient.so twice leads to a segfault in libmirprotobuf.so
        (LP: #1391976)
      . Visible corruption in SDL apps (LP: #1460149)
      . MultiThreadedCompositor::destroy_compositing_threads hangs/deadlocks on
        shutdown or display reconfiguration (LP: #1471909)
      . ctest/"make test" reports 100% tests pass even when some fail.
        (LP: #1472911)
      . Mir server crashed - GLib-CRITICAL **: g_source_get_context: assertion
       'source->context != NULL || !SOURCE_DESTROYED (source)' failed
        (LP: #1473869)
      . USC crash on multimonitor unplug [std::exception::what: error during
        hwc prepare()] (LP: #1474891)
      . [regression] Input focus delay after switching app back into focus
        (LP: #1480654)
      . GLibMainLoopTest.propagates_exception_from_server_action fails with
        GCC 5 in armhf (LP: #1482274)
      . [enhancement] Mir lacks relative mouse support (LP: #1276322)
      . ShmBuffer ignores pixel_format (LP: #1424909)
      . Fullscreen bypassed clients stutter with double buffers when other
        clients are running (LP: #1447896)
      . [regression] Demo servers crash on start-up if MIR_ENABLE_TESTS=OFF
        (LP: #1439078)
      . [regression] The software curs...