This is of particular interest to WebView since we run in other people's processes and the lack of supporting this might actually make the tool less effective for apps, but is probably interesting in general to catch actual errors in our code. I think this is something we would want to have, though I'm not sure what priority we would consider it to have. If you are interested in implementing this for us then I doubt we'd be against it, though :)

I'm switching the type to Task because it's not a user-facing feature, though; internal code improvements generally are tracked there.

We are still using the crazy linker. I'm not sure what that implies for weak symbols/etc.

Adding Andrew and Tommy for any additional comments (may want a general base owner also since this is going to involve adding more parts there; dunno who would be the best person to ask about this though)

Maybe gab@ or dcheng@ would be interested in this? Adding them to CC in case they want to be involved.

I agree that this looks like something we'd want for Chrome.

I started on an implementation yesterday and fell into a pile of SFINAE goop for detecting when to enable this. It seems much easier to just use an explicit tag type that the traits must inherit from to enable the Acquire/Release tracking, so I implemented that instead.

One additional complication is that ScopedGeneric::receive is fundamentally incompatible with this. I hid that method when using the ownership tracking stuff, but I'm not sure whether there are any actual uses of ScopedFD::receive. I tried to code search for it, but the signal to noise ratio wasn't great. I'll just implement AndroidScopedFDCloseTraits tomorrow and see what happens...

CL at https://chromium-review.googlesource.com/c/chromium/src/+/1224112

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/00ce84541f824dbf1ae1860193415227254dba07

commit 00ce84541f824dbf1ae1860193415227254dba07
Author: Josh Gao <jmgao@google.com>
Date: Wed Oct 31 00:05:42 2018

ScopedGeneric: add support for ownership tracking.

Add support for ScopedGeneric traits that track the ownership of owned
objects externally. The intent is to use this with Android Q's file
descriptor ownership sanitizer, but this is conceivably useful for
other purposes as well (e.g. guarded_fd on Darwin).

TBR=wez@chromium.org,sergeyu@chromium.org,alexilin@chromium.org,vollick@chromium.org,dcastagna@chromium.org

Bug:  882733 
Change-Id: I2fb0617ce6471b290edcc726de4117041d91d10d
Reviewed-on: https://chromium-review.googlesource.com/c/1224112
Commit-Queue: Josh Gao <jmgao@google.com>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604067}
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/base/fuchsia/file_utils.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/base/memory/platform_shared_memory_region_mac.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/base/metrics/field_trial_memory_mac.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/base/metrics/field_trial_memory_mac_unittest.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/base/scoped_generic.h
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/base/scoped_generic_unittest.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/chrome/browser/android/vr/arcore_device/arcore_impl.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/components/exo/wayland/clients/client_base.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/mojo/core/channel_fuchsia.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/mojo/core/channel_posix.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/ui/ozone/platform/drm/gpu/hardware_display_plane_manager_atomic.cc
[modify] https://crrev.com/00ce84541f824dbf1ae1860193415227254dba07/ui/ozone/platform/drm/gpu/hardware_display_plane_manager_atomic.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/913a828a460849b6a2a9eac8a206bcdb4008f3e3

commit 913a828a460849b6a2a9eac8a206bcdb4008f3e3
Author: Josh Gao <jmgao@google.com>
Date: Wed Oct 31 00:49:39 2018

Use fdsan on Android.

When available, use ScopedGeneric's ownership tracking to guard its
file descriptors with fdsan.

Bug:  882733 
Change-Id: Ibe600465d6bb7e3032e23ed813dea3d8f8ededa8
Reviewed-on: https://chromium-review.googlesource.com/c/1225309
Commit-Queue: Josh Gao <jmgao@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604083}
[modify] https://crrev.com/913a828a460849b6a2a9eac8a206bcdb4008f3e3/base/BUILD.gn
[modify] https://crrev.com/913a828a460849b6a2a9eac8a206bcdb4008f3e3/base/files/scoped_file.h
[add] https://crrev.com/913a828a460849b6a2a9eac8a206bcdb4008f3e3/base/files/scoped_file_android.cc