Comment 1 for bug 1270685

(gdb) bt
#0 0xb65c9724 in __libc_do_syscall ()
   from /lib/arm-linux-gnueabihf/libpthread.so.0
#1 0xb65c52e6 in pthread_cond_wait@@GLIBC_2.4 ()
   from /lib/arm-linux-gnueabihf/libpthread.so.0
#2 0xb64b7654 in std::condition_variable::wait(std::unique_lock<std::mutex>&)
    () from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#3 0xb6dbc350 in mir::compositor::SwitchingBundle::client_acquire (
    this=0x21e64e8)
    at /home/dan/bzr/mir/dev/src/server/compositor/switching_bundle.cpp:213
#4 0xb6db3a1a in mir::compositor::BufferStreamSurfaces::swap_client_buffers (
    this=0x21a1bf8, buffer=@0x222c2cc: 0x21d2788)
    at /home/dan/bzr/mir/dev/src/server/compositor/buffer_stream_surfaces.cpp:58
#5 0xb6e1d3b8 in mir::scene::BasicSurface::swap_buffers (this=0x21a1c28,
    buffer=@0x222c2cc: 0x21d2788)
    at /home/dan/bzr/mir/dev/src/server/scene/basic_surface.cpp:121
#6 0xb6e408ba in mir::scene::SurfaceImpl::swap_buffers (this=0x21a2648,
    buffer=@0x222c2cc: 0x21d2788)
    at /home/dan/bzr/mir/dev/src/server/scene/surface_impl.cpp:108
#7 0xb6de2432 in mir::frontend::ForwardingInternalSurface::swap_buffers (
    this=0x21a1c88, buffer=@0x222c2cc: 0x21d2788)
    at /home/dan/bzr/mir/dev/src/server/frontend/surface.cpp:42
#8 0xb694818c in mir::graphics::android::InternalClientWindow::driver_returns_---Type <return> to continue, or q <return> to quit---
buffer (this=0x222c2c0, key=0x2229820, fence_fd=-1)
    at /home/dan/bzr/mir/dev/src/platform/graphics/android/internal_client_window.cpp:68
#9 0xb694f66a in mir::graphics::android::MirNativeWindow::cancelBuffer (
    this=0x21b6c60, buffer=0x2229820, fence=-1)
    at /home/dan/bzr/mir/dev/src/shared/graphics/android/mir_native_window.cpp:186
#10 0xb694f456 in (anonymous namespace)::cancelBuffer_static (
    window=0x21b6c60, buffer=0x2229820, fence_fd=-1)
    at /home/dan/bzr/mir/dev/src/shared/graphics/android/mir_native_window.cpp:121