Add ScopedTaskSuspend and its test

Add ScopedTaskSuspend and its test.

This also introduces ScopedFcntlFlags.

TEST=util_test ScopedTaskSuspend.*:ScopedFcntlFlags.*
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/2bd5e23ea49d8a7160bbdab403652fdd2f25086c

[Mark Mentovai, 2014-10-10 17:03:51]

mark@chromium.org changed reviewers:
+ rsesek@chromium.org

[Robert Sesek, 2014-10-13 15:01:37]

https://codereview.chromium.org/649693002/diff/1/util/mach/scoped_task_suspen...
File util/mach/scoped_task_suspend_test.cc (right):

https://codereview.chromium.org/649693002/diff/1/util/mach/scoped_task_suspen...
util/mach/scoped_task_suspend_test.cc:39: static int CounterValue(TaskMemory*
task_memory, mach_vm_address_t address) {
Does this test really need to use TaskMemory? Could you instead test if the task
suspension works by merely messaging over the shared pipe instead?

[Mark Mentovai, 2014-10-13 16:35:34]

Like this?

[Robert Sesek, 2014-10-13 19:09:39]

I think the test is better because it's relying on time less, but it'd be best
to not do that at all. Right now the test is testing that a kernel API is doing
that it says it does (suspend a task), rather than just the scoper aspect. Per
offline discussion, can we instead just take the kernel interface at face value
and use task_info() to see if the task is suspended?

https://codereview.chromium.org/649693002/diff/150002/util/posix/scoped_fcntl...
File util/posix/scoped_fcntl_flags.h (right):

https://codereview.chromium.org/649693002/diff/150002/util/posix/scoped_fcntl...
util/posix/scoped_fcntl_flags.h:26: ScopedFcntlFlags(int fd, int set_flags, int
clear_flags);
Should document how |clear_flags| works.

https://codereview.chromium.org/649693002/diff/150002/util/posix/scoped_fcntl...
File util/posix/scoped_fcntl_flags_test.cc (right):

https://codereview.chromium.org/649693002/diff/150002/util/posix/scoped_fcntl...
util/posix/scoped_fcntl_flags_test.cc:34: PCHECK(rv != -1) << "fcntl";
Use EXPECT_ instead so you don't crash the test?

[Mark Mentovai, 2014-10-13 20:23:27]

Patchset #5 (id:280001) has been deleted

[Mark Mentovai, 2014-10-13 20:24:32]

Updated per feedback.

[Robert Sesek, 2014-10-13 21:34:51]

LGTM

[Mark Mentovai, 2014-10-13 22:05:28]

Committed patchset #6 (id:420001) manually as
2bd5e23ea49d8a7160bbdab403652fdd2f25086c (presubmit successful).