Add and use scoped-right-returning wrappers for Mach bootstrap routines

Add and use scoped-right-returning wrappers for Mach bootstrap routines

This wraps bootstrap_check_in() in BootstrapCheckIn(), and
bootstrap_look_up() in BootstrapLookUp(). The wrappers make it more
difficult to accidentally leak a returned right. They’re easier to use,
encapsulating common error checking and logging, simplifying all call
sites.

TEST=crashpad_util_test MachExtensions.BootstrapCheckInAndLookUp
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/bb13efbda7ef55bde9a4afa870b4155ead78cd45

[Mark Mentovai, 2015-10-05 17:15:55]

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

[Robert Sesek, 2015-10-05 19:00:20]

LGTM

https://codereview.chromium.org/1383283003/diff/20001/util/mach/mach_extensio...
File util/mach/mach_extensions.cc (right):

https://codereview.chromium.org/1383283003/diff/20001/util/mach/mach_extensio...
util/mach/mach_extensions.cc:39: const char BootstrapCheckInTraits::kName[] =
"bootstrap_check_in";
In C++11 this can't be initialized in the struct itself?

[Mark Mentovai, 2015-10-05 19:33:03]

https://codereview.chromium.org/1383283003/diff/20001/util/mach/mach_extensio...
File util/mach/mach_extensions.cc (right):

https://codereview.chromium.org/1383283003/diff/20001/util/mach/mach_extensio...
util/mach/mach_extensions.cc:39: const char BootstrapCheckInTraits::kName[] =
"bootstrap_check_in";
Robert Sesek wrote:
> In C++11 this can't be initialized in the struct itself?

I wish.

mach_extensions.cc:37:21: error: in-class initializer for static data member of
type 'const char [19]' requires 'constexpr' specifier

constexpr shows up on the banned list,
https://chromium-cpp.appspot.com/#blacklist_banned. But even if it didn’t, we’d
need to provide storage:

Undefined symbols for architecture x86_64:
  "(anonymous namespace)::BootstrapLookUpTraits::kName", referenced from:
      crashpad::BootstrapLookUp(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&) in
libcrashpad_util.a(crashpad_util.mach_extensions.o)

So it’s not much help. We can write

    static const char kName[];
  };
  const char BootstrapCheckInTraits::kName[] = "bootstrap_check_in";

or the banned

    static constexpr char kName[] = "bootstrap_check_in";
  };
  constexpr char BootstrapCheckInTraits::kName[];

[Mark Mentovai, 2015-10-05 21:07:20]

Committed patchset #2 (id:20001) manually as
bb13efbda7ef55bde9a4afa870b4155ead78cd45 (presubmit successful).