Make breakpad work in the seccomp sandbox. Take advantage of a feature in linux_syscall_support.h that allows us to mark all places where we embedd direct system calls. This allows the sandbox to rewrite them as needed.
Make breakpad work in the seccomp sandbox. Take advantage of a feature
in linux_syscall_support.h that allows us to mark all places where we
embedd direct system calls. This allows the sandbox to rewrite them as
needed.

Also mark a few system calls as having ignored return codes. This makes
some compilers happy and prevents warning messages.

Finally, add more verbose error messages if crashdumping fails. There are
various reasons why breakpad can be prevented from doing its job. And
these error messages have proven helpful. We should leave them in the
production binary.

TEST=add --enable-seccomp-mode to command line and go to about:crash
BUG=37728
Review URL: http://codereview.chromium.org/3122028

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@56694 0039d316-1c4b-4281-b951-d872f2087c98

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